diff --git a/core/MAINTAINERS.txt b/core/MAINTAINERS.txt
index 75d48e4..d479f08 100644
--- a/core/MAINTAINERS.txt
+++ b/core/MAINTAINERS.txt
@@ -242,6 +242,9 @@ Path module
 PHP module
 - ?
 
+Picture module
+- Peter Droogmans 'attiks' http://drupal.org/user/105002
+
 Poll module
 - Andrei Mateescu 'amateescu' http://drupal.org/user/729614
 
diff --git a/core/includes/common.inc b/core/includes/common.inc
index 4c86953..540f42b 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -3759,15 +3759,15 @@ function drupal_region_class($region) {
  *       else being the same, JavaScript added by a call to drupal_add_js() that
  *       happened later in the page request gets added to the page after one for
  *       which drupal_add_js() happened earlier in the page request.
- *   - defer: If set to TRUE, the defer attribute is set on the <script>
- *     tag. Defaults to FALSE.
- *   - async: If set to TRUE, the async attribute is set on the <script>
- *     tag. Defaults to FALSE.
  *   - cache: If set to FALSE, the JavaScript file is loaded anew on every page
  *     call; in other words, it is not cached. Used only when 'type' references
  *     a JavaScript file. Defaults to TRUE.
  *   - preprocess: If TRUE and JavaScript aggregation is enabled, the script
  *     file will be aggregated. Defaults to TRUE.
+ *   - attributes: An associative array of attributes for the <script> tag. This
+ *     may be used to add 'defer', 'async', or custom attributes. Note that
+ *     setting any attributes will disable preprocessing as though the
+ *     'preprocess' option was set to FALSE.
  *   - browsers: An array containing information specifying which browsers
  *     should load the JavaScript item. See
  *     drupal_pre_render_conditional_comments() for details.
@@ -3793,8 +3793,8 @@ function drupal_add_js($data = NULL, $options = NULL) {
   }
   $options += drupal_js_defaults($data);
 
-  // Preprocess can only be set if caching is enabled.
-  $options['preprocess'] = $options['cache'] ? $options['preprocess'] : FALSE;
+  // Preprocess can only be set if caching is enabled and no attributes are set.
+  $options['preprocess'] = $options['cache'] && empty($options['attributes']) ? $options['preprocess'] : FALSE;
 
   // Tweak the weight so that files of the same weight are included in the
   // order of the calls to drupal_add_js().
@@ -3861,9 +3861,8 @@ function drupal_js_defaults($data = NULL) {
     'weight' => 0,
     'scope' => 'header',
     'cache' => TRUE,
-    'defer' => FALSE,
-    'async' => FALSE,
     'preprocess' => TRUE,
+    'attributes' => array(),
     'version' => NULL,
     'data' => $data,
     'browsers' => array(),
@@ -4090,16 +4089,9 @@ function drupal_pre_render_scripts($elements) {
             break;
         }
 
-        // The defer and async attributes must not be specified if the src
-        // attribute is not present.
-        if (!empty($element['#attributes']['src'])) {
-          // Both may be specified for legacy browser fallback purposes.
-          if (!empty($item['async'])) {
-            $element['#attributes']['async'] = 'async';
-          }
-          if (!empty($item['defer'])) {
-            $element['#attributes']['defer'] = 'defer';
-          }
+        // Attributes may only be set if this script is output independently.
+        if (!empty($element['#attributes']['src']) && !empty($item['attributes'])) {
+          $element['#attributes'] += $item['attributes'];
         }
 
         $elements[] = $element;
@@ -5807,6 +5799,9 @@ function drupal_render_children(&$element, $children_keys = NULL) {
  * @see hide()
  */
 function render(&$element) {
+  if (!$element && $element !== 0) {
+    return NULL;
+  }
   if (is_array($element)) {
     show($element);
     return drupal_render($element);
@@ -6886,8 +6881,9 @@ function drupal_flush_all_caches() {
   drupal_container()->get('router.builder')->rebuild();
   menu_router_rebuild();
 
-  // Wipe the DIC cache.
+  // Wipe the PHP Storage caches.
   drupal_php_storage('service_container')->deleteAll();
+  drupal_php_storage('twig')->deleteAll();
 
   // Re-initialize the maintenance theme, if the current request attempted to
   // use it. Unlike regular usages of this function, the installer and update
diff --git a/core/includes/menu.inc b/core/includes/menu.inc
index 0f97cf4..d28316b 100644
--- a/core/includes/menu.inc
+++ b/core/includes/menu.inc
@@ -1638,7 +1638,7 @@ function theme_menu_local_task($variables) {
     $link_text = t('!local-task-title!active', array('!local-task-title' => $link['title'], '!active' => $active));
   }
 
-  return '<li' . (!empty($variables['element']['#active']) ? ' class="active"' : '') . '>' . l($link_text, $link['href'], $link['localized_options']) . "</li>\n";
+  return '<li' . (!empty($variables['element']['#active']) ? ' class="active"' : '') . '>' . l($link_text, $link['href'], $link['localized_options']) . '</li>';
 }
 
 /**
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 0c35b90..d2fe902 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -229,6 +229,12 @@ function _drupal_theme_initialize($theme, $base_theme = array(), $registry_callb
       include_once DRUPAL_ROOT . '/' . $theme->owner;
     }
   }
+  // Load twig as secondary always available engine.
+  // @todo Make twig the default engine and remove this. This is required
+  // because (by design) the theme system doesn't allow modules to register more
+  // than one type of extension. We need a temporary backwards compatibility
+  // layer to allow us to perform core-wide .tpl.php to .twig conversion.
+  include_once DRUPAL_ROOT . '/core/themes/engines/twig/twig.engine';
 
   if (isset($registry_callback)) {
     _theme_registry_callback($registry_callback, array($theme, $base_theme, $theme_engine));
@@ -468,6 +474,28 @@ function _theme_process_registry(&$cache, $name, $type, $theme, $path) {
         if (!isset($info['path'])) {
           $result[$hook]['template'] = $path . '/templates/' . $info['template'];
         }
+        if ($type == 'module') {
+          // Add two render engines for modules.
+          // @todo Remove and make twig the default engine.
+          $render_engines = array(
+            '.twig' => 'twig',
+            '.tpl.php' => 'phptemplate'
+          );
+
+          // Find the best engine for this template.
+          foreach ($render_engines as $extension => $engine) {
+            // Render the output using the template file.
+            $template_file = $result[$hook]['template'] . $extension;
+            if (isset($info['path'])) {
+              $template_file = $info['path'] . '/' . $template_file;
+            }
+            if (file_exists($template_file)) {
+              $result[$hook]['template_file'] = $template_file;
+              $result[$hook]['engine'] = $engine;
+              break;
+            }
+          }
+        }
       }
 
       // Allow variable processors for all theming hooks, whether the hook is
@@ -1054,6 +1082,11 @@ function theme($hook, $variables = array()) {
           $extension = $extension_function();
         }
       }
+      elseif (isset($info['engine'])) {
+        if (function_exists($info['engine'] . '_render_template')) {
+          $render_function = $info['engine'] . '_render_template';
+        }
+      }
     }
 
     // In some cases, a template implementation may not have had
@@ -1077,6 +1110,12 @@ function theme($hook, $variables = array()) {
     if (isset($info['path'])) {
       $template_file = $info['path'] . '/' . $template_file;
     }
+
+    // Modules can override this.
+    if (isset($info['template_file'])) {
+      $template_file = $info['template_file'];
+    }
+
     $output = $render_function($template_file, $variables);
   }
 
@@ -1252,7 +1291,14 @@ function drupal_find_theme_templates($cache, $extension, $path) {
       $matches = preg_grep('/^' . $pattern . '/', $patterns);
       if ($matches) {
         foreach ($matches as $match) {
-          $file = substr($match, 0, strpos($match, '.'));
+          $file = $match;
+          // Chop off the remaining extensions if there are any. $template
+          // already has the rightmost extension removed, but there might still
+          // be more, such as with .tpl.php, which still has .tpl in $template
+          // at this point.
+          if (($pos = strpos($match, '.')) !== FALSE) {
+            $file = substr($match, 0, $pos);
+          }
           // Put the underscores back in for the hook name and register this pattern.
           $arg_name = isset($info['variables']) ? 'variables' : 'render element';
           $implementations[strtr($file, '-', '_')] = array(
@@ -2915,6 +2961,7 @@ function drupal_common_theme() {
     ),
     'datetime' => array(
       'variables' => array('timestamp' => NULL, 'text' => NULL, 'attributes' => array(), 'html' => FALSE),
+      'template' => 'datetime',
     ),
     'status_messages' => array(
       'variables' => array('display' => NULL),
diff --git a/core/lib/Drupal/Core/Access/AccessCheckInterface.php b/core/lib/Drupal/Core/Access/AccessCheckInterface.php
new file mode 100644
index 0000000..0ce0abb
--- /dev/null
+++ b/core/lib/Drupal/Core/Access/AccessCheckInterface.php
@@ -0,0 +1,40 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Access\AccessCheckInterface.
+ */
+
+namespace Drupal\Core\Access;
+
+use Symfony\Component\Routing\Route;
+
+/**
+ * A access check service determines access rules for particular routes.
+ */
+interface AccessCheckInterface {
+
+  /**
+   * Declares whether the access check applies to a specific route or not.
+   *
+   * @param Symfony\Component\Routing\Route $route
+   *    The route to consider attaching to.
+   *
+   * @return boolean
+   *    True if check applies to passed route, false if not.
+   */
+  public function applies(Route $route);
+
+  /**
+   * Checks for access to route.
+   *
+   * @param Symfony\Component\Routing\Route $route
+   *    The route to check against.
+   *
+   * @return mixed
+   *    TRUE if access is allowed.
+   *    FALSE if not.
+   *    NULL if no opinion.
+   */
+  public function access(Route $route);
+}
diff --git a/core/lib/Drupal/Core/Access/AccessManager.php b/core/lib/Drupal/Core/Access/AccessManager.php
new file mode 100644
index 0000000..2c487f9
--- /dev/null
+++ b/core/lib/Drupal/Core/Access/AccessManager.php
@@ -0,0 +1,134 @@
+<?php
+/**
+ * @file
+ * Definition of Drupal\Core\Access\AccessManager.
+ */
+
+namespace Drupal\Core\Access;
+
+use Symfony\Component\Routing\RouteCollection;
+use Symfony\Component\Routing\Route;
+use Symfony\Component\DependencyInjection\ContainerAware;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+
+/**
+ * Attaches access checks services to routes and runs them on request.
+ */
+class AccessManager extends ContainerAware {
+
+  /**
+   * Array of registered access check service ids.
+   *
+   * @var array
+   */
+  protected $checkIds;
+
+  /**
+   * Array of access check objects keyed by service id.
+   *
+   * @var array
+   */
+  protected $checks;
+
+  /**
+   * Registers a new AccessCheck by service ID.
+   *
+   * @param string $service_id
+   *   The ID of the service in the Container that provides a check.
+   */
+  public function addCheckService($service_id) {
+    $this->checkIds[] = $service_id;
+  }
+
+  /**
+   * For each route, saves a list of applicable access checks to the route.
+   *
+   * @param RouteCollection $routes
+   *    A collection of routes to apply checks to.
+   */
+  public function setChecks(RouteCollection $routes) {
+    foreach ($routes as $route) {
+      $checks = $this->applies($route);
+      if (!empty($checks)) {
+        $route->setOption('_access_checks', $checks);
+      }
+    }
+  }
+
+  /**
+   * Determine which registered access checks apply to a route.
+   *
+   * @param Symfony\Component\Routing\Route $route
+   *    The route to get list of access checks for.
+   *
+   * @return array
+   *    An array of service ids for the access checks that apply to passed
+   *    route.
+   */
+  protected function applies(Route $route) {
+    $checks = array();
+
+    foreach ($this->checkIds as $service_id) {
+      if (empty($this->checks[$service_id])) {
+        $this->loadCheck($service_id);
+      }
+
+      if ($this->checks[$service_id]->applies($route)) {
+        $checks[] = $service_id;
+      }
+    }
+
+    return $checks;
+  }
+
+  /**
+   * Check route against applicable access check services to determine whether
+   * it is accessible.
+   *
+   * @param Symfony\Component\Routing\Route $route
+   *    The route to check access to.
+   *
+   * @throws Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException
+   *    If any access check denies access or none explicitly approve.
+   */
+  public function check(Route $route) {
+    $access = FALSE;
+    $checks = $route->getOption('_access_checks');
+
+    // No checks == deny by default.
+    if (!empty($checks)) {
+      foreach ($checks as $service_id) {
+        if (empty($this->checks[$service_id])) {
+          $this->loadCheck($service_id);
+        }
+
+        $access = $this->checks[$service_id]->access($route);
+        if ($access === FALSE) {
+          // A check has denied access, no need to continue checking.
+          break;
+        }
+      }
+    }
+
+    // Access has been denied or not explicily approved.
+    if (!$access) {
+      throw new AccessDeniedHttpException();
+    }
+  }
+
+  /**
+   * Lazy-loads access check services.
+   *
+   * @param string $service_id
+   *    The service id of the access check service to load.
+   */
+  protected function loadCheck($service_id) {
+    if (!in_array($service_id, $this->checkIds)) {
+      throw new \InvalidArgumentException(sprintf('No check has been registered for %s', $service_id));
+    }
+
+    $this->checks[$service_id] = $this->container->get($service_id);
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Access/DefaultAccessCheck.php b/core/lib/Drupal/Core/Access/DefaultAccessCheck.php
new file mode 100644
index 0000000..4dc53f7
--- /dev/null
+++ b/core/lib/Drupal/Core/Access/DefaultAccessCheck.php
@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Access\DefaultAccessCheck.
+ */
+
+namespace Drupal\Core\Access;
+
+use Symfony\Component\Routing\Route;
+
+/**
+ * Allows access to routes to be controlled by an '_access' boolean parameter.
+ */
+class DefaultAccessCheck implements AccessCheckInterface {
+
+  /**
+   * Declares whether the access check applies to a specific route or not.
+   *
+   * @param Symfony\Component\Routing\Route $route
+   *    The route to consider attaching to.
+   *
+   * @return boolean
+   *    True if check applies to passed route, false if not.
+   */
+  public function applies(Route $route) {
+    return $route->hasDefault('_access');
+  }
+
+  /**
+   * Checks for access to route.
+   *
+   * @param Symfony\Component\Routing\Route $route
+   *    The route to check against.
+   *
+   * @return mixed
+   *    TRUE if access is allowed.
+   *    FALSE if not.
+   *    NULL if no opinion.
+   */
+  public function access(Route $route) {
+    return $route->getDefault('_access');
+  }
+}
diff --git a/core/lib/Drupal/Core/Access/PermissionAccessCheck.php b/core/lib/Drupal/Core/Access/PermissionAccessCheck.php
new file mode 100644
index 0000000..89e5fbd
--- /dev/null
+++ b/core/lib/Drupal/Core/Access/PermissionAccessCheck.php
@@ -0,0 +1,49 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Access\PermissionAccessCheck.
+ */
+
+namespace Drupal\Core\Access;
+
+use Symfony\Component\Routing\Route;
+
+/**
+ * Determines access to routes based on permissions defined via hook_permission().
+ */
+class PermissionAccessCheck implements AccessCheckInterface {
+
+  /**
+   * Declares whether the access check applies to a specific route or not.
+   * Applies to a route if it has a '_permission' property set.
+   *
+   * @param Symfony\Component\Routing\Route $route
+   *    The route to consider attaching to.
+   *
+   * @return boolean
+   *    True if check applies to passed route, false if not.
+   */
+  public function applies(Route $route) {
+    return $route->hasDefault('_permission');
+  }
+
+  /**
+   * Checks for access to route.
+   *
+   * @param Symfony\Component\Routing\Route $route
+   *    The route to check against.
+   *
+   * @return mixed
+   *    TRUE if access is allowed.
+   *    FALSE if not.
+   *    NULL if no opinion.
+   */
+  public function access(Route $route) {
+    $permission = $route->getDefault('_permission');
+    // @todo Replace user_access() with a correctly injected and session-using
+    //   alternative.
+    // If user_access() fails, return NULL to give other checks a chance.
+    return user_access($permission) ? TRUE : NULL;
+  }
+}
diff --git a/core/lib/Drupal/Core/CoreBundle.php b/core/lib/Drupal/Core/CoreBundle.php
index 5a07c55..64a0422 100644
--- a/core/lib/Drupal/Core/CoreBundle.php
+++ b/core/lib/Drupal/Core/CoreBundle.php
@@ -8,6 +8,7 @@
 namespace Drupal\Core;
 
 use Drupal\Core\DependencyInjection\Compiler\RegisterKernelListenersPass;
+use Drupal\Core\DependencyInjection\Compiler\RegisterAccessChecksPass;
 use Drupal\Core\DependencyInjection\Compiler\RegisterMatchersPass;
 use Drupal\Core\DependencyInjection\Compiler\RegisterNestedMatchersPass;
 use Symfony\Component\DependencyInjection\Definition;
@@ -59,6 +60,9 @@ public function build(ContainerBuilder $container) {
     $container->register('user.tempstore', 'Drupal\user\TempStoreFactory')
       ->addArgument(new Reference('database'))
       ->addArgument(new Reference('lock'));
+    $container->register('twig', 'Drupal\Core\Template\TwigEnvironment')
+      ->setFactoryClass('Drupal\Core\Template\TwigFactory')
+      ->setFactoryMethod('get');
 
     // Add the entity query factory.
     $container->register('entity.query', 'Drupal\Core\Entity\Query\QueryFactory')
@@ -67,8 +71,11 @@ public function build(ContainerBuilder $container) {
     $container->register('router.dumper', 'Drupal\Core\Routing\MatcherDumper')
       ->addArgument(new Reference('database'));
     $container->register('router.builder', 'Drupal\Core\Routing\RouteBuilder')
+      ->addArgument(new Reference('dispatcher'))
       ->addArgument(new Reference('router.dumper'))
-      ->addArgument(new Reference('lock'));
+      ->addArgument(new Reference('lock'))
+      ->addArgument(new Reference('dispatcher'));
+
 
     $container->register('matcher', 'Drupal\Core\Routing\ChainMatcher');
     $container->register('legacy_url_matcher', 'Drupal\Core\LegacyUrlMatcher')
@@ -99,8 +106,17 @@ public function build(ContainerBuilder $container) {
     $container->register('view_subscriber', 'Drupal\Core\EventSubscriber\ViewSubscriber')
       ->addArgument(new Reference('content_negotiation'))
       ->addTag('event_subscriber');
+    $container->register('legacy_access_subscriber', 'Drupal\Core\EventSubscriber\LegacyAccessSubscriber')
+      ->addTag('event_subscriber');
+    $container->register('access_manager', 'Drupal\Core\Access\AccessManager')
+      ->addMethodCall('setContainer', array(new Reference('service_container')));
     $container->register('access_subscriber', 'Drupal\Core\EventSubscriber\AccessSubscriber')
+      ->addArgument(new Reference('access_manager'))
       ->addTag('event_subscriber');
+    $container->register('access_check.default', 'Drupal\Core\Access\DefaultAccessCheck')
+      ->addTag('access_check');
+    $container->register('access_check.permission', 'Drupal\Core\Access\PermissionAccessCheck')
+      ->addTag('access_check');
     $container->register('maintenance_mode_subscriber', 'Drupal\Core\EventSubscriber\MaintenanceModeSubscriber')
       ->addTag('event_subscriber');
     $container->register('path_subscriber', 'Drupal\Core\EventSubscriber\PathSubscriber')
@@ -127,6 +143,8 @@ public function build(ContainerBuilder $container) {
     $container->addCompilerPass(new RegisterNestedMatchersPass());
     // Add a compiler pass for registering event subscribers.
     $container->addCompilerPass(new RegisterKernelListenersPass(), PassConfig::TYPE_AFTER_REMOVING);
+
+    $container->addCompilerPass(new RegisterAccessChecksPass());
   }
 
 }
diff --git a/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterAccessChecksPass.php b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterAccessChecksPass.php
new file mode 100644
index 0000000..0ae3585
--- /dev/null
+++ b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterAccessChecksPass.php
@@ -0,0 +1,22 @@
+<?php
+
+/**
+ * @file
+ */
+
+namespace Drupal\Core\DependencyInjection\Compiler;
+
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
+
+class RegisterAccessChecksPass implements CompilerPassInterface {
+  public function process(ContainerBuilder $container) {
+    if (!$container->hasDefinition('access_manager')) {
+      return;
+    }
+    $access_manager = $container->getDefinition('access_manager');
+    foreach ($container->findTaggedServiceIds('access_check') as $id => $attributes) {
+      $access_manager->addMethodCall('AddCheckService', array($id));
+    }
+  }
+}
diff --git a/core/lib/Drupal/Core/EventSubscriber/AccessSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/AccessSubscriber.php
index 4f1dc75..8d50414 100644
--- a/core/lib/Drupal/Core/EventSubscriber/AccessSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/AccessSubscriber.php
@@ -11,6 +11,9 @@
 use Symfony\Component\HttpKernel\Event\GetResponseEvent;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+use Drupal\Core\Routing\RoutingEvents;
+use Drupal\Core\Routing\Event\RoutesEvent;
+use Drupal\Core\Access\AccessManager;
 
 /**
  * Access subscriber for controller requests.
@@ -18,21 +21,41 @@
 class AccessSubscriber implements EventSubscriberInterface {
 
   /**
-   * Verifies that the current user can access the requested path.
+   * Constructs a new AccessCheckManager.
    *
-   * @todo This is a total hack to keep our current access system working. It
-   *   should be replaced with something robust and injected at some point.
+   * @param AccessCheckManager $access_check_manager
+   *   The access check manager that will be responsible for applying
+   *   AccessCheckers against routes.
+   */
+  public function __construct(AccessManager $access_manager) {
+    $this->accessManager = $access_manager;
+  }
+
+  /**
+   * Verifies that the current user can access the requested path.
    *
    * @param Symfony\Component\HttpKernel\Event\GetResponseEvent $event
    *   The Event to process.
    */
   public function onKernelRequestAccessCheck(GetResponseEvent $event) {
+    $request = $event->getRequest();
+    if (!$request->attributes->has('_route')) {
+      // If no Route is available it is likely a static resource and access is
+      // handled elsewhere.
+      return;
+    }
 
-    $router_item = $event->getRequest()->attributes->get('drupal_menu_item');
+    $this->accessManager->check($request->attributes->get('_route'));
+  }
 
-    if (isset($router_item['access']) && !$router_item['access']) {
-      throw new AccessDeniedHttpException();
-    }
+  /**
+   * Apply access checks to routes.
+   *
+   * @param Drupal\Core\Routing\Event\RoutesEvent $event
+   *    The event to process.
+   */
+  public function onRoutingRouteAlterSetAccessCheck(RoutesEvent $event) {
+    $this->accessManager->setChecks($event->getRoutes());
   }
 
   /**
@@ -43,6 +66,8 @@ public function onKernelRequestAccessCheck(GetResponseEvent $event) {
    */
   static function getSubscribedEvents() {
     $events[KernelEvents::REQUEST][] = array('onKernelRequestAccessCheck', 30);
+    // Setting very low priority to ensure access checks are run after alters.
+    $events[RoutingEvents::ROUTE_ALTER][] = array('onRoutingRouteAlterSetAccessCheck', 0);
 
     return $events;
   }
diff --git a/core/lib/Drupal/Core/EventSubscriber/LegacyAccessSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/LegacyAccessSubscriber.php
new file mode 100644
index 0000000..707de62
--- /dev/null
+++ b/core/lib/Drupal/Core/EventSubscriber/LegacyAccessSubscriber.php
@@ -0,0 +1,49 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\EventSubscriber\LegacyAccessSubscriber.
+ */
+
+namespace Drupal\Core\EventSubscriber;
+
+use Symfony\Component\HttpKernel\KernelEvents;
+use Symfony\Component\HttpKernel\Event\GetResponseEvent;
+use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+/**
+ * Access subscriber for legacy controller requests.
+ */
+class LegacyAccessSubscriber implements EventSubscriberInterface {
+
+  /**
+   * Verifies that the current user can access the requested path.
+   *
+   * @todo This is a total hack to keep our current access system working. It
+   *   should be replaced with something robust and injected at some point.
+   *
+   * @param Symfony\Component\HttpKernel\Event\GetResponseEvent $event
+   *   The Event to process.
+   */
+  public function onKernelRequestAccessCheck(GetResponseEvent $event) {
+
+    $router_item = $event->getRequest()->attributes->get('drupal_menu_item');
+
+    if (isset($router_item['access']) && !$router_item['access']) {
+      throw new AccessDeniedHttpException();
+    }
+  }
+
+  /**
+   * Registers the methods in this class that should be listeners.
+   *
+   * @return array
+   *   An array of event listener definitions.
+   */
+  static function getSubscribedEvents() {
+    $events[KernelEvents::REQUEST][] = array('onKernelRequestAccessCheck', 30);
+
+    return $events;
+  }
+}
diff --git a/core/lib/Drupal/Core/Routing/Event/RoutesEvent.php b/core/lib/Drupal/Core/Routing/Event/RoutesEvent.php
new file mode 100644
index 0000000..3dff57e
--- /dev/null
+++ b/core/lib/Drupal/Core/Routing/Event/RoutesEvent.php
@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Routing\Event\RoutesEvent.
+ */
+
+namespace Drupal\Core\Routing\Event;
+
+use Symfony\Component\EventDispatcher\Event;
+use Symfony\Component\Routing\RouteCollection;
+
+/**
+ * Event fired when a collection of routes have been added to the route builder
+ * and are about to be saved.
+ */
+class RoutesEvent extends Event {
+
+  /**
+   * A collection of routes about to be saved.
+   * @var Symfony\Component\Routing\RouteCollection
+   */
+  private $routes;
+
+  public function __construct(RouteCollection $routes) {
+    $this->routes = $routes;
+  }
+
+  /**
+   * Returns the routes that are about to be saved.
+   *
+   * @return Symfony\Component\Routing\RouteCollection
+   */
+  public function getRoutes() {
+    return $this->routes;
+  }
+}
diff --git a/core/lib/Drupal/Core/Routing/FirstEntryFinalMatcher.php b/core/lib/Drupal/Core/Routing/FirstEntryFinalMatcher.php
index 45d0888..cc1adde 100644
--- a/core/lib/Drupal/Core/Routing/FirstEntryFinalMatcher.php
+++ b/core/lib/Drupal/Core/Routing/FirstEntryFinalMatcher.php
@@ -53,7 +53,8 @@ public function matchRequest(Request $request) {
 
       preg_match($compiled->getRegex(), $path, $matches);
 
-      return array_merge($this->mergeDefaults($matches, $route->getDefaults()), array('_route' => $name));
+      $route->setOption('_name', $name);
+      return array_merge($this->mergeDefaults($matches, $route->getDefaults()), array('_route' => $route));
     }
   }
 
diff --git a/core/lib/Drupal/Core/Routing/RouteBuildEvent.php b/core/lib/Drupal/Core/Routing/RouteBuildEvent.php
new file mode 100644
index 0000000..9f16bcb
--- /dev/null
+++ b/core/lib/Drupal/Core/Routing/RouteBuildEvent.php
@@ -0,0 +1,46 @@
+<?php
+
+namespace Drupal\Core\Routing;
+
+use Symfony\Component\EventDispatcher\Event;
+use Symfony\Component\Routing\RouteCollection;
+
+class RouteBuildEvent extends Event {
+
+  /**
+   * The route collection.
+   *
+   * @var Symfony\Component\Routing\RouteCollection
+   */
+  protected $routeCollection;
+
+  /**
+   * The module name.
+   *
+   * @var string
+   */
+  protected $module;
+
+  /**
+   * Constructor.
+   */
+  public function __construct(RouteCollection $route_collection, $module) {
+    $this->routeCollection = $route_collection;
+    $this->module = $module;
+  }
+
+  /**
+   * Get the route collection.
+   */
+  public function getRouteCollection() {
+    return $this->routeCollection;
+  }
+
+  /**
+   * Get the module.
+   */
+  public function getModule() {
+    return $this->module;
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Routing/RouteBuilder.php b/core/lib/Drupal/Core/Routing/RouteBuilder.php
index 3a27767..67ff034 100644
--- a/core/lib/Drupal/Core/Routing/RouteBuilder.php
+++ b/core/lib/Drupal/Core/Routing/RouteBuilder.php
@@ -7,8 +7,15 @@
 
 namespace Drupal\Core\Routing;
 
-use Drupal\Core\Lock\LockBackendInterface;
 use Symfony\Component\Routing\Matcher\Dumper\MatcherDumperInterface;
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
+use Symfony\Component\Routing\RouteCompilerInterface;
+use Symfony\Component\Routing\Route;
+use Symfony\Component\Yaml\Parser;
+use Symfony\Component\Routing\RouteCollection;
+use Drupal\Core\Routing\Event\RoutesEvent;
+
+use Drupal\Core\Lock\LockBackendInterface;
 
 /**
  * Managing class for rebuilding the router table.
@@ -33,16 +40,29 @@ class RouteBuilder {
   protected $lock;
 
   /**
+   * The event dispatcher to notify of routes.
+   *
+   * @var Symfony\Component\EventDispatcher\EventDispatcherInterface
+   */
+  protected $dispatcher;
+
+  /**
    * Construcs the RouteBuilder using the passed MatcherDumperInterface.
    *
+   * @param \Symfony\Component\EventDispatcher\EventDispatcherInterface $dispatcher
+   *   The dispatcher used to dispatch events.
    * @param \Symfony\Component\Routing\Matcher\Dumper\MatcherDumperInterface $dumper
    *   The matcher dumper used to store the route information.
    * @param \Drupal\Core\Lock\LockBackendInterface $lock
    *   The lock backend.
+   * @param \Symfony\Component\EventDispatcherEventDispatcherInterface
+   *   The event dispatcher to notify of routes.
    */
-  public function __construct(MatcherDumperInterface $dumper, LockBackendInterface $lock) {
+  public function __construct(EventDispatcherInterface $dispatcher, MatcherDumperInterface $dumper, LockBackendInterface $lock) {
+    $this->dispatcher = $dispatcher;
     $this->dumper = $dumper;
     $this->lock = $lock;
+    $this->dispatcher = $dispatcher;
   }
 
   /**
@@ -57,15 +77,38 @@ public function rebuild() {
       return;
     }
 
+    $parser = new Parser();
+
     // We need to manually call each module so that we can know which module
     // a given item came from.
-
-    foreach (module_implements('route_info') as $module) {
-      $routes = call_user_func($module . '_route_info');
-      drupal_alter('router_info', $routes, $module);
-      $this->dumper->addRoutes($routes);
+    // @todo Use an injected Extension service rather than module_list():
+    //   http://drupal.org/node/1331486.
+    foreach (module_list() as $module) {
+      $collection = new RouteCollection();
+      $routing_file = DRUPAL_ROOT . '/' . drupal_get_path('module', $module) . '/' . $module . '.routing.yml';
+      if (file_exists($routing_file)) {
+        $routes = $parser->parse(file_get_contents($routing_file));
+        if (!empty($routes)) {
+          foreach ($routes as $name => $route_info) {
+            $defaults = isset($route_info['defaults']) ? $route_info['defaults'] : array();
+            $requirements = isset($route_info['requirements']) ? $route_info['requirements'] : array();
+            $route = new Route($route_info['pattern'], $defaults, $requirements);
+            $collection->add($name, $route);
+          }
+        }
+      }
+      $this->eventDispatcher->dispatch(RoutingEvents::ALTER, new RouteBuildEvent($collection, $module));
+      $this->dumper->addRoutes($collection);
       $this->dumper->dump(array('route_set' => $module));
     }
+
+    // Now allow modules to register additional, dynamic routes.
+    $collection = new RouteCollection();
+    $this->eventDispatcher->dispatch(RoutingEvents::DYNAMIC, new RouteBuildEvent($collection, 'dynamic_routes'));
+    $this->eventDispatcher->dispatch(RoutingEvents::ALTER, new RouteBuildEvent($collection, 'dynamic_routes'));
+    $this->dumper->addRoutes($collection);
+    $this->dumper->dump(array('route_set' => $module));
+
     $this->lock->release('router_rebuild');
   }
 
diff --git a/core/lib/Drupal/Core/Routing/RoutingEvents.php b/core/lib/Drupal/Core/Routing/RoutingEvents.php
new file mode 100644
index 0000000..6a72ff0
--- /dev/null
+++ b/core/lib/Drupal/Core/Routing/RoutingEvents.php
@@ -0,0 +1,38 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Routing\RoutingEvents.
+ */
+
+namespace Drupal\Core\Routing;
+
+/**
+ * Contains all events thrown in the core routing component.
+ */
+final class RoutingEvents {
+
+  /**
+   * The ALTER event is fired on a route collection to allow changes to routes.
+   *
+   * This event is used to process new routes before they get saved.
+   *
+   * @see Drupal\Core\Routing\RouteBuildEvent
+   *
+   * @var string
+   */
+  const ALTER = 'routing.route_alter';
+
+  /**
+   * The DYNAMIC event is fired to allow modules to register additional routes.
+   *
+   * Most routes are static, an should be defined as such. Dynamic routes are
+   * only those whose existence changes depending on the state of the system
+   * at runtime, depending on configuration.
+   *
+   * @see Drupal\Core\Routing\RouteBuildEvent
+   *
+   * @var string
+   */
+  const DYNAMIC = 'routing.route_dynamic';
+}
diff --git a/core/lib/Drupal/Core/Template/TwigEnvironment.php b/core/lib/Drupal/Core/Template/TwigEnvironment.php
new file mode 100644
index 0000000..bc7ab65
--- /dev/null
+++ b/core/lib/Drupal/Core/Template/TwigEnvironment.php
@@ -0,0 +1,100 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Template\TwigEnvironment.
+ */
+
+namespace Drupal\Core\Template;
+
+/**
+ * A class that defines a Twig environment for Drupal.
+ *
+ * Instances of this class are used to store the configuration and extensions,
+ * and are used to load templates from the file system or other locations.
+ *
+ * @see core\vendor\twig\twig\lib\Twig\Enviornment.php
+ */
+class TwigEnvironment extends \Twig_Environment {
+  protected $cache_object = NULL;
+  protected $storage = NULL;
+
+  /**
+   * Constructs a TwigEnvironment object and stores cache and storage
+   * internally.
+   */
+  public function __construct(\Twig_LoaderInterface $loader = NULL, $options = array()) {
+    // @todo Pass as arguments from the DIC?
+    $this->cache_object = cache();
+    $this->storage = drupal_php_storage('twig');
+
+    parent::__construct($loader, $options);
+  }
+
+  /**
+   * Checks if the compiled template needs an update.
+   */
+  public function needsUpdate($cache_filename, $name) {
+     $cid = 'twig:' . $cache_filename;
+     $obj = $this->cache_object->get($cid);
+     $mtime = isset($obj->data) ? $obj->data : FALSE;
+     return $mtime !== FALSE && !$this->isTemplateFresh($name, $mtime);
+  }
+
+  /**
+   * Compile the source and write the compiled template to disk.
+   */
+  public function updateCompiledTemplate($cache_filename, $name) {
+    $source = $this->loader->getSource($name);
+    $compiled_source = $this->compileSource($source, $name);
+    $this->storage->save($cache_filename, $compiled_source);
+    // Save the last modification time
+    $cid = 'twig:' . $cache_filename;
+    $this->cache_object->set($cid, REQUEST_TIME);
+  }
+
+  /**
+   * Implements Twig_Environment::loadTemplate().
+   *
+   * We need to overwrite this function to integrate with drupal_php_storage().
+   *
+   * This is a straight copy from loadTemplate() changed to use
+   * drupal_php_storage().
+   */
+  public function loadTemplate($name, $index = NULL) {
+    $cls = $this->getTemplateClass($name, $index);
+
+    if (isset($this->loadedTemplates[$cls])) {
+      return $this->loadedTemplates[$cls];
+    }
+
+    if (!class_exists($cls, FALSE)) {
+      $cache_filename = $this->getCacheFilename($name);
+
+      if ($cache_filename === FALSE) {
+        $source = $this->loader->getSource($name);
+        $compiled_source = $this->compileSource($source, $name);
+        eval('?' . '>' . $compiled_source);
+      } else {
+
+        // If autoreload is on, check that the template has not been
+        // modified since the last compilation.
+        if ($this->isAutoReload() && $this->needsUpdate($cache_filename, $name)) {
+          $this->updateCompiledTemplate($cache_filename, $name);
+        }
+
+        if (!$this->storage->load($cache_filename)) {
+          $this->updateCompiledTemplate($cache_filename, $name);
+          $this->storage->load($cache_filename);
+        }
+      }
+    }
+
+    if (!$this->runtimeInitialized) {
+        $this->initRuntime();
+    }
+
+    return $this->loadedTemplates[$cls] = new $cls($this);
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Template/TwigFactory.php b/core/lib/Drupal/Core/Template/TwigFactory.php
new file mode 100644
index 0000000..ef1a40d
--- /dev/null
+++ b/core/lib/Drupal/Core/Template/TwigFactory.php
@@ -0,0 +1,98 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Template\TwigFactory.
+ *
+ * This provides a factory class to construct Twig_Environment objects and use
+ * them in combination with the Drupal Injection Container.
+ *
+ * @see \Drupal\Core\CoreBundle
+ */
+
+namespace Drupal\Core\Template;
+
+/**
+ * A class for constructing Twig_Environment objects.
+ *
+ * This is used for constructing and configuring a system wide Twig_Environment
+ * object that is integrated with the Drupal Injection Container.
+ *
+ * @see \Drupal\Core\CoreBundle
+ */
+class TwigFactory {
+  /**
+  * Returns a fully initialized Twig_Environment object.
+  *
+  * This constructs and configures a Twig_Environment. It also adds Drupal
+  * specific Twig_NodeVisitors, filters and functions.
+  *
+  * To retrieve the system wide Twig_Environment object you should use:
+  * @code
+  *   $twig = drupal_container()->get('twig');
+  * @endcode
+  * This will retrieve the Twig_Environment object from the DIC.
+  *
+  * @return Twig_Environment
+  *   The fully initialized Twig_Environment object.
+  *
+  * @see twig_render
+  * @see TwigNodeVisitor
+  * @see TwigReference
+  * @see TwigReferenceFunction
+  */
+  public static function get() {
+    // @todo Maybe we will have our own loader later.
+    $loader = new \Twig_Loader_Filesystem(DRUPAL_ROOT);
+    $twig = new TwigEnvironment($loader, array(
+        // This is saved / loaded via drupal_php_storage().
+        // All files can be refreshed by clearing caches.
+        // @todo ensure garbage collection of expired files.
+        'cache' => TRUE,
+        'base_template_class' => 'Drupal\Core\Template\TwigTemplate',
+        // @todo Remove in followup issue
+        // @see http://drupal.org/node/1712444.
+        'autoescape' => FALSE,
+        // @todo Remove in followup issue
+        // @see http://drupal.org/node/1806538.
+        'strict_variables' => FALSE,
+        // @todo Maybe make debug mode dependent on "production mode" setting.
+        'debug' => TRUE,
+        // @todo Make auto reload mode dependent on "production mode" setting.
+        'auto_reload' => FALSE,
+    ));
+
+    // The node visitor is needed to wrap all variables with
+    // render -> twig_render() function.
+    $twig->addNodeVisitor(new TwigNodeVisitor());
+    $twig->addTokenParser(new TwigFunctionTokenParser('hide'));
+    $twig->addTokenParser(new TwigFunctionTokenParser('show'));
+
+    // @todo Figure out what to do about debugging functions.
+    // @see http://drupal.org/node/1804998
+    $twig->addExtension(new \Twig_Extension_Debug());
+
+    $reference_functions = array(
+      'hide' => 'twig_hide',
+      'render' => 'twig_render',
+      'show' => 'twig_show',
+      // @todo re-add unset => twig_unset if this is really needed
+    );
+    $filters = array(
+      't' => 't'
+    );
+
+    // These functions will receive a TwigReference object, if a render array is detected
+    foreach ($reference_functions as $function => $php_function) {
+      $twig->addFunction($function, new TwigReferenceFunction($php_function));
+    }
+
+    foreach ($filters as $filter => $php_function) {
+      $twig->addFilter($filter, new \Twig_Filter_Function($php_function));
+    }
+
+    // @todo Remove URL function once http://drupal.org/node/1778610 is resolved.
+    $twig->addFunction('url', new \Twig_Function_Function('url'));
+    return $twig;
+  }
+}
diff --git a/core/lib/Drupal/Core/Template/TwigFunctionTokenParser.php b/core/lib/Drupal/Core/Template/TwigFunctionTokenParser.php
new file mode 100644
index 0000000..2d123cc
--- /dev/null
+++ b/core/lib/Drupal/Core/Template/TwigFunctionTokenParser.php
@@ -0,0 +1,60 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Template\TwigFunctionTokenParser.
+ */
+
+namespace Drupal\Core\Template;
+
+/**
+ * A class that defines the Twig token parser for Drupal.
+ *
+ * The token parser converts a token stream created from template source
+ * code into an Abstract Syntax Tree (AST).  The AST will later be compiled
+ * into PHP code usable for runtime execution of the template.
+ *
+ * @see core\vendor\twig\twig\lib\Twig\TokenParser.php
+ */
+class TwigFunctionTokenParser extends \Twig_TokenParser {
+
+  /**
+   * The name of tag. Can be 'hide' or 'show'.
+   *
+   * @var string
+   */
+  protected $tag;
+
+  /**
+   * Constructor for TwigFunctionTokenParser.
+   *
+   * Locally scope variables.
+   */
+  public function __construct($tag = 'hide') {
+    $this->tag = $tag;
+  }
+
+  /**
+   * Parses a token and returns a node.
+   *
+   * @param Twig_Token $token A Twig_Token instance.
+   *
+   * @return Twig_Node_Print A Twig_Node_Print instance.
+   */
+  public function parse(\Twig_Token $token) {
+    $lineno = $token->getLine();
+
+    $expr = $this->parser->getExpressionParser()->parseExpression();
+    $this->parser->getStream()->expect(\Twig_Token::BLOCK_END_TYPE);
+    return new \Twig_Node_Print(new \Twig_Node_Expression_Function($this->tag, new \Twig_Node(array($expr)), $lineno), $lineno);
+  }
+
+  /**
+   * Gets the tag name associated with this token parser.
+   *
+   * @return string The tag name
+   */
+  public function getTag() {
+    return $this->tag;
+  }
+}
diff --git a/core/lib/Drupal/Core/Template/TwigNodeExpressionNameReference.php b/core/lib/Drupal/Core/Template/TwigNodeExpressionNameReference.php
new file mode 100644
index 0000000..c66d73f
--- /dev/null
+++ b/core/lib/Drupal/Core/Template/TwigNodeExpressionNameReference.php
@@ -0,0 +1,29 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Template\TwigNodeExpressionNameReference
+ */
+
+namespace Drupal\Core\Template;
+
+/**
+ * A class that defines a reference to the name for all nodes that represent
+ * expressions.
+ *
+ * @see core\vendor\twig\twig\lib\Twig\Node\Expression\Name.php
+ */
+class TwigNodeExpressionNameReference extends \Twig_Node_Expression_Name {
+
+  /**
+   * Overrides Twig_Node_Expression_Name::compile().
+   */
+  public function compile(\Twig_Compiler $compiler) {
+    $name = $this->getAttribute('name');
+    $compiler
+    ->raw('$this->getContextReference($context, ')
+    ->string($name)
+    ->raw(')');
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Template/TwigNodeVisitor.php b/core/lib/Drupal/Core/Template/TwigNodeVisitor.php
new file mode 100644
index 0000000..0cf5465
--- /dev/null
+++ b/core/lib/Drupal/Core/Template/TwigNodeVisitor.php
@@ -0,0 +1,95 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Template\TwigNodeVisitor.
+ */
+
+namespace Drupal\Core\Template;
+
+/**
+ * Provides a Twig_NodeVisitor to change the generated parse-tree.
+ *
+ * This is used to ensure that everything that is printed is wrapped via
+ * twig_render() function so that we can write for example just {{ content }}
+ * in templates instead of having to write {{ render(content) }}.
+ *
+ * @see twig_render
+ */
+class TwigNodeVisitor implements \Twig_NodeVisitorInterface {
+
+  /**
+   * TRUE when this node is a function getting arguments by reference.
+   *
+   * For example: 'hide' or 'render' are such functions.
+   *
+   * @var bool
+   */
+  protected $isReference = FALSE;
+
+  /**
+   * Implements Twig_NodeVisitorInterface::enterNode().
+   */
+  function enterNode(\Twig_NodeInterface $node, \Twig_Environment $env) {
+   if ($node instanceof \Twig_Node_Expression_Function) {
+      $name = $node->getAttribute('name');
+      $func = $env->getFunction($name);
+
+      // Optimization: Do not support nested functions.
+      if ($this->isReference && $func instanceof \Twig_Function_Function) {
+        $this->isReference = FALSE;
+      }
+      if ($func instanceof TwigReferenceFunction) {
+        // We need to create a TwigReference
+        $this->isReference = TRUE;
+      }
+    }
+    if ($node instanceof \Twig_Node_Print) {
+       // Our injected render needs arguments passed by reference -- in case of render array
+      $this->isReference = TRUE;
+    }
+
+    return $node;
+  }
+
+  /**
+   * Implements Twig_NodeVisitorInterface::leaveNode().
+   *
+   * We use this to inject a call to render -> twig_render()
+   * before anything is printed.
+   *
+   * @see twig_render
+   */
+  function leaveNode(\Twig_NodeInterface $node, \Twig_Environment $env) {
+    if ($node instanceof \Twig_Node_Print) {
+      $this->isReference = FALSE;
+
+      $class = get_class($node);
+      return new $class(
+        new \Twig_Node_Expression_Function('render', new \Twig_Node(array($node->getNode('expr'))), $node->getLine()),
+        $node->getLine()
+      );
+    }
+
+    if ($this->isReference) {
+      if ($node instanceof \Twig_Node_Expression_Name) {
+        $name = $node->getAttribute('name');
+        return new TwigNodeExpressionNameReference($name, $node->getLine());
+      }
+      elseif ($node instanceof \Twig_Function_Function) {
+        // Do something!
+        $this->isReference = FALSE;
+      }
+    }
+
+    return $node;
+  }
+
+  /**
+   * Implements Twig_NodeVisitorInterface::getPriority().
+   */
+  function getPriority() {
+    // We want to run before other NodeVisitors like Escape or Optimizer
+    return -1;
+  }
+}
diff --git a/core/lib/Drupal/Core/Template/TwigReference.php b/core/lib/Drupal/Core/Template/TwigReference.php
new file mode 100644
index 0000000..0b8b506
--- /dev/null
+++ b/core/lib/Drupal/Core/Template/TwigReference.php
@@ -0,0 +1,131 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Template\TwigReference.
+ */
+
+namespace Drupal\Core\Template;
+
+/**
+ * A class used to pass variables by reference while they are used in twig.
+ *
+ * This is done by saving a reference to the original render array within a
+ * TwigReference via the setReference() method like this:
+ * @code
+ * $obj = new TwigReference();
+ * $obj->setReference($variable);
+ * @endcode
+ *
+ * When a TwigReference is accessed via the offsetGet method the resulting
+ * reference is again wrapped within a TwigReference. Therefore references to
+ * render arrays within render arrays are also retained.
+ *
+ * To unwrap TwigReference objects the reference can be retrieved out of the
+ * object by calling the getReference() method like this:
+ * @code
+ * $variable = &$obj->getReference();
+ * @endcode
+ * This allows render(), hide() and show() to access the original variable and
+ * change it. The process of unwrapping and passing by reference to this
+ * functions is done transparently by the TwigReferenceFunctions helper class.
+ *
+ * @see TwigReferenceFunction
+ * @see TwigReferenceFunctions
+ */
+class TwigReference extends \ArrayObject {
+
+  /**
+   * Holds an internal reference to the original array.
+   *
+   * @var array
+   */
+  protected $writableRef = array();
+
+  /**
+   * Constructs a \Drupal\Core\Template\TwigReference object.
+   *
+   * The argument to the constructor is ignored as it is not safe that this will
+   * always be a reference.
+   *
+   * To set a reference use:
+   * @code
+   * $obj = new TwigReference();
+   * $obj->setReference($variable);
+   * @endcode
+   *
+   * @param $array
+   *   The array parameter is ignored and not passed to the parent
+   */
+  public function __construct($array = NULL) {
+    parent::__construct();
+  }
+
+  /**
+   * Sets a reference in the internal storage.
+   *
+   * @param $array
+   *   The array to set as internal reference.
+   */
+  public function setReference(&$array) {
+    $this->exchangeArray($array);
+    $this->writableRef = &$array;
+  }
+
+  /**
+   * Gets a reference to the internal storage.
+   *
+   * Should be called like:
+   * @code
+   * $reference = &$obj->getReference();
+   * @endcode
+   *
+   * @return
+   *   Returns the stored internal reference.
+   */
+  public function &getReference() {
+    return $this->writableRef;
+  }
+
+  /**
+   * Sets offset in internal reference and internal storage to value.
+   *
+   * This is just for completeness, but should never be used, because
+   * twig cannot set properties and should not.
+   *
+   * @link http://php.net/manual/en/arrayaccess.offsetset.php
+   * @param mixed $offset
+   *   The offset to assign the value to.
+   * @param mixed $value
+   *   The value to set.
+   */
+  public function offsetSet($offset, $value) {
+    $this->writableRef[$offset] = $value;
+    parent::offsetSet($offset, $value);
+  }
+
+  /**
+   * Retrieves offset from internal reference.
+   *
+   * In case of a render array, it is wrapped again within a TwigReference
+   * object.
+   *
+   * @param mixed $offset
+   *   The offset to retrieve.
+   *
+   * @return mixed
+   *   Returns a TwigReference object wrapping the array if the retrieved offset
+   *   is a complex array (i.e. not an attribute). Else it returns the retrived
+   *   offset directly.
+   */
+  public function offsetGet($offset) {
+    if (!is_array($this->writableRef[$offset]) || $offset[0] == '#') {
+      return $this->writableRef[$offset];
+    }
+
+    // Wrap the returned array in a new TwigReference.
+    $x = clone $this; // clone is faster than new
+    $x->setReference($this->writableRef[$offset]);
+    return $x;
+  }
+}
diff --git a/core/lib/Drupal/Core/Template/TwigReferenceFunction.php b/core/lib/Drupal/Core/Template/TwigReferenceFunction.php
new file mode 100644
index 0000000..6ca4cbd
--- /dev/null
+++ b/core/lib/Drupal/Core/Template/TwigReferenceFunction.php
@@ -0,0 +1,14 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Template\TwigReferenceFunction.
+ */
+
+namespace Drupal\Core\Template;
+
+/**
+ * This class is used to create functions requiring references like 'hide'.
+ */
+class TwigReferenceFunction extends \Twig_Function_Function {
+}
diff --git a/core/lib/Drupal/Core/Template/TwigReferenceFunctions.php b/core/lib/Drupal/Core/Template/TwigReferenceFunctions.php
new file mode 100644
index 0000000..4f584d1
--- /dev/null
+++ b/core/lib/Drupal/Core/Template/TwigReferenceFunctions.php
@@ -0,0 +1,93 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Template\TwigReferenceFunctions.
+ */
+
+namespace Drupal\Core\Template;
+
+/**
+ * A helper used to unwrap TwigReference objects transparently.
+ *
+ * This is providing a static magic function that makes it easier to unwrap
+ * TwigReference objects and pass variables by reference to show(), hide() and
+ * render().
+ *
+ * The problem is that twig passes variables only by value. The following is a
+ * simplified version of the generated code by twig when the property "links" of
+ * a render array stored in $content should be hidden:
+ * @code
+ * $_content_ = $content;
+ * hide(getAttribute($_content_, 'links'));
+ * @endcode
+ * As hide() is operating on a copy of the original array the hidden property
+ * is not set on the original $content variable.
+ *
+ * TwigReferenceFunctions can be used in combination with TwigReference to solve
+ * this problem:
+ * @code
+ * // Internally getContextReference returns the array wrapped in a
+ * // TwigReference if certain criteria are met
+ * function getContextReference(&$content) {
+ *   $obj = new Drupal\Core\Template\TwigReference();
+ *   $obj->setReference($content);
+ *   return $obj;
+ * }
+ *
+ * // [...]
+ * // Simplified, generated twig code
+ * $_content_ = getContextReference($content);
+ *
+ * Drupal\Core\Template\TwigReferenceFunctions::hide(
+ *   getAttribute($_content_, 'links')
+ * );
+ * @endcode
+ * A TwigReference object is passed to the __callStatic function of
+ * TwigReferenceFunctions. The method unwraps the TwigReference and calls the
+ * hide() method essentially with a reference to $content['links'].
+ *
+ * Therefore the hidden property is correctly set and a successive call to
+ * render() will not render the content twice.
+ *
+ * @see TwigReference
+ * @see TwigReferenceFunction
+ * @see TwigFactory
+ *
+ */
+class TwigReferenceFunctions {
+
+  /**
+   * Magic function to call functions called from twig templates with a
+   * reference to the original variable.
+   *
+   * This checks if the array provided by value is containing a reference to
+   * the original version. If yes it replaces the argument with its reference.
+   *
+   * @param $name
+   *   The name of the function to call.
+   * @param $arguments
+   *   The arguments to process and pass to the called function.
+   *
+   * @return mixed
+   *   Returns the output of the called function.
+   *
+   * @see TwigReference
+  */
+  public static function __callStatic($name, $arguments) {
+    foreach ($arguments as $key => $val) {
+      if (is_object($val) && $val instanceof TwigReference) {
+        $arguments[$key] = &$val->getReference();
+      }
+    }
+
+    // Needed to pass by reference -- could also restrict to maximum one
+    // argument instead
+    $args = array();
+    foreach ($arguments as $key => &$arg) {
+      $args[$key] = &$arg;
+    }
+
+    return call_user_func_array($name, $args);
+  }
+}
diff --git a/core/lib/Drupal/Core/Template/TwigTemplate.php b/core/lib/Drupal/Core/Template/TwigTemplate.php
new file mode 100644
index 0000000..7d7eeca
--- /dev/null
+++ b/core/lib/Drupal/Core/Template/TwigTemplate.php
@@ -0,0 +1,81 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Template\TwigTemplate.
+ */
+
+namespace Drupal\Core\Template;
+
+/**
+ * This is the base class for compiled Twig templates.
+ */
+abstract class TwigTemplate extends \Twig_Template {
+
+  /**
+   * A class used to pass variables by reference while they are used in Twig.
+   */
+  protected $twig_reference = NULL;
+
+  /**
+   * List of the name of variables to be passed around as references.
+   *
+   * @var array
+   */
+  protected $is_reference = array();
+
+  /**
+   * List of the name of variables to be passed around by value.
+   *
+   * @var array
+   */
+  protected $is_no_reference = array();
+
+  /**
+   * @param array $context
+   *   The variables available to the template.
+   * @param $item
+   *   The name of the variable.
+   * @return mixed
+   *   The requested variable.
+   */
+  final protected function getContextReference(&$context, $item)
+  {
+    // Optimized version
+    if (!isset($context[$item])) {
+      // We don't want to throw an exception, but issue a warning instead.
+      // This is the easiest way to do so.
+      // @todo Decide based on prod vs. dev setting
+      $msg = new \Twig_Error(t('@item could not be found in _context', array('@item' => $item)));
+      trigger_error($msg->getMessage(), E_USER_WARNING);
+      return NULL;
+    }
+
+    // The first test also finds empty / null render arrays
+    if (!$context[$item] || isset($this->is_no_reference[$item])) {
+      return $context[$item];
+    }
+
+    if (isset($context['_references'][$item])) {
+      return $context['_references'][$item];
+    }
+
+    // @todo Check if this is a render array (existence of #theme?)
+    if ((!isset($this->is_reference[$item])) && ($context[$item] instanceof \TwigMarkup || !is_array($context[$item]))) {
+      $this->is_no_reference[$item] = TRUE;
+      return $context[$item];
+    }
+
+    if ($this->twig_reference == NULL) {
+      $this->twig_reference = new TwigReference();
+    }
+    $ref = clone $this->twig_reference; // clone is _much_ faster than new
+    $ref->setReference($context[$item]);
+
+    // Save that this is a reference
+    $context['_references'][$item] = $ref;
+    $this->is_reference[$item] = TRUE;
+
+    return $ref;
+  }
+}
diff --git a/core/modules/image/config/image.settings.yml b/core/modules/image/config/image.settings.yml
new file mode 100644
index 0000000..c6dadc8
--- /dev/null
+++ b/core/modules/image/config/image.settings.yml
@@ -0,0 +1 @@
+preview_image: core/modules/image/sample.png
diff --git a/core/modules/image/image.admin.inc b/core/modules/image/image.admin.inc
index ca55227..933a4ad 100644
--- a/core/modules/image/image.admin.inc
+++ b/core/modules/image/image.admin.inc
@@ -697,7 +697,7 @@ function theme_image_style_effects($variables) {
 function theme_image_style_preview($variables) {
   $style = $variables['style'];
 
-  $sample_image = variable_get('image_style_preview_image', drupal_get_path('module', 'image') . '/sample.png');
+  $sample_image = config('image.settings')->get('preview_image');
   $sample_width = 160;
   $sample_height = 160;
 
diff --git a/core/modules/image/image.install b/core/modules/image/image.install
index 88f05a1..e4e77d8 100644
--- a/core/modules/image/image.install
+++ b/core/modules/image/image.install
@@ -167,3 +167,14 @@ function image_update_8001() {
   db_drop_table('image_styles');
   db_drop_table('image_effects');
 }
+
+/**
+ * Moves image module settings from variable to config.
+ *
+ * @ingroup config_upgrade
+ */
+function image_update_8002() {
+  update_variables_to_config('image.settings', array(
+    'image_style_preview_image' => 'preview_image',
+  ));
+}
diff --git a/core/modules/layout/layouts/static/one-col/one-col.tpl.php b/core/modules/layout/layouts/static/one-col/one-col.tpl.php
new file mode 100644
index 0000000..61af832
--- /dev/null
+++ b/core/modules/layout/layouts/static/one-col/one-col.tpl.php
@@ -0,0 +1,18 @@
+<?php
+/**
+ * @file
+ * Template for a 1 column layout.
+ *
+ * This template provides a simple one column display layout.
+ *
+ * Variables:
+ * - $content: An array of content, each item in the array is keyed to one
+ *   region of the layout. This layout supports only one section:
+ *   - $content['content']: Content in the content column.
+ */
+?>
+<div class="layout-display layout-one-col <?php print $attributes['class']; ?>"<?php print $attributes; ?>>
+  <div class="layout-region">
+    <?php print $content['content']; ?>
+  </div>
+</div>
diff --git a/core/modules/layout/layouts/static/one-col/one-col.yml b/core/modules/layout/layouts/static/one-col/one-col.yml
new file mode 100644
index 0000000..deaa7f8
--- /dev/null
+++ b/core/modules/layout/layouts/static/one-col/one-col.yml
@@ -0,0 +1,5 @@
+title: One column
+category: Columns: 1
+template: one-col
+regions:
+  content: 'Content'
diff --git a/core/modules/layout/layouts/static/twocol/two-col-rtl.css b/core/modules/layout/layouts/static/twocol/two-col-rtl.css
new file mode 100644
index 0000000..0fe6a0a
--- /dev/null
+++ b/core/modules/layout/layouts/static/twocol/two-col-rtl.css
@@ -0,0 +1,6 @@
+/* Large resolutions (desktop, tablets in landscape, ...) */
+@media only screen and (min-width: 59em) {
+  .layout-two-col .layout-region {
+    float: right;
+  }
+}
diff --git a/core/modules/layout/layouts/static/twocol/two-col.css b/core/modules/layout/layouts/static/twocol/two-col.css
new file mode 100644
index 0000000..bb7ae25
--- /dev/null
+++ b/core/modules/layout/layouts/static/twocol/two-col.css
@@ -0,0 +1,7 @@
+/* Large resolutions (desktop, tablets in landscape, ...) */
+@media only screen and (min-width: 59em) {
+  .layout-two-col .layout-region {
+    float: left; /* LTR */
+    width: 50%;
+  }
+}
diff --git a/core/modules/layout/layouts/static/twocol/two-col.tpl.php b/core/modules/layout/layouts/static/twocol/two-col.tpl.php
new file mode 100644
index 0000000..810a052
--- /dev/null
+++ b/core/modules/layout/layouts/static/twocol/two-col.tpl.php
@@ -0,0 +1,24 @@
+<?php
+/**
+ * @file
+ * Template for a 2 column layout.
+ *
+ * This template provides a two column display layout, with each column equal in
+ * width.
+ *
+ * Variables:
+ * - $content: An array of content, each item in the array is keyed to one
+ *   region of the layout. This layout supports the following sections:
+ *   - $content['first']: Content in the first column.
+ *   - $content['second']: Content in the second column.
+ */
+?>
+<div class="layout-display layout-two-col clearfix <?php print $attributes['class']; ?>"<?php print $attributes; ?>>
+  <div class="layout-region layout-col-first">
+    <?php print $content['first']; ?>
+  </div>
+
+  <div class="layout-region layout-col-second">
+    <?php print $content['second']; ?>
+  </div>
+</div>
diff --git a/core/modules/layout/layouts/static/twocol/two-col.yml b/core/modules/layout/layouts/static/twocol/two-col.yml
new file mode 100644
index 0000000..e4aef7e
--- /dev/null
+++ b/core/modules/layout/layouts/static/twocol/two-col.yml
@@ -0,0 +1,9 @@
+title: Two column
+category: Columns: 2
+template: two-col
+stylesheets:
+  - two-col.css
+  - two-col-rtl.css
+regions:
+  first: 'First column'
+  second: 'Second column'
diff --git a/core/modules/layout/lib/Drupal/layout/Tests/LayoutDerivativesTest.php b/core/modules/layout/lib/Drupal/layout/Tests/LayoutDerivativesTest.php
index 1071713..0766838 100644
--- a/core/modules/layout/lib/Drupal/layout/Tests/LayoutDerivativesTest.php
+++ b/core/modules/layout/lib/Drupal/layout/Tests/LayoutDerivativesTest.php
@@ -37,7 +37,7 @@ function testDerivatives() {
 
     $definitions = $manager->getDefinitions();
     $this->assertTrue(is_array($definitions), 'Definitions found.');
-    $this->assertTrue(count($definitions) == 2, 'Two definitions available.');
+    $this->assertTrue(count($definitions) == 4, 'Four definitions available.');
     $this->assertTrue(isset($definitions['static_layout:layout_test__one-col']), 'One column layout found.');
     $this->assertTrue(isset($definitions['static_layout:layout_test_theme__two-col']), 'Two column layout found.');
 
diff --git a/core/modules/layout/tests/layout_test.module b/core/modules/layout/tests/layout_test.module
index 36c3915..52ab4a3 100644
--- a/core/modules/layout/tests/layout_test.module
+++ b/core/modules/layout/tests/layout_test.module
@@ -9,6 +9,7 @@
  * Implementation of hook_menu().
  */
 function layout_test_menu() {
+  $items = array();
   $items['layout-test'] = array(
     'title' => 'Layout test',
     'page callback' => 'layout_test_page',
diff --git a/core/modules/node/templates/node.twig b/core/modules/node/templates/node.twig
new file mode 100644
index 0000000..2d4a674
--- /dev/null
+++ b/core/modules/node/templates/node.twig
@@ -0,0 +1,106 @@
+{#
+/**
+ * @file
+ * Default theme implementation to display a node.
+ *
+ * Available variables:
+ * - label: the title of the node.
+ * - content: node items. Use {{ content }} to print them all,
+ *   or print a subset such as {{ content.field_example }}. Use
+ *   {% hide(content.field_example) %} to temporarily suppress the printing
+ *   of a given element.
+ * - user_picture: The node author's picture from user-picture.twig.
+ * - date: Formatted creation date. Preprocess functions can reformat it by
+ *   calling format_date() with the desired parameters on
+ *   $variables['created'].
+ * - name: Themed username of node author output from theme_username().
+ * - node_url: Direct URL of the current node.
+ * - display_submitted: Whether submission information should be displayed.
+ * - submitted: Submission information created from name and date during
+ *   template_preprocess_node().
+ * - attributes: HTML attributes for the surrounding element.
+ *    Attributes include the 'class' information, which contains:
+ *   - node: The current template type; for example, "theming hook".
+ *   - node-[type]: The current node type. For example, if the node is a
+ *     "Article" it would result in "node-article". Note that the machine
+ *     name will often be in a short form of the human readable label.
+ *   - view-mode-[view_mode]: The View Mode of the node; for example, "teaser"
+ *     or "full".
+ *   - preview: Nodes in preview mode.
+ *   The following are controlled through the node publishing options.
+ *   - promoted: Nodes promoted to the front page.
+ *   - sticky: Nodes ordered above other non-sticky nodes in teaser
+ *     listings.
+ *   - unpublished: Unpublished nodes visible only to administrators.
+ * - title_prefix: Additional output populated by modules, intended to be
+ *   displayed in front of the main title tag that appears in the template.
+ * - title_suffix: Additional output populated by modules, intended to be
+ *   displayed after the main title tag that appears in the template.
+ *
+ * Other variables:
+ * - node: Fully loaded node entity.
+ * - type: Node type; for example, page, article, etc.
+ * - comment_count: Number of comments attached to the node.
+ * - uid: User ID of the node author.
+ * - created: Time the node was published formatted as a Unix timestamp.
+ * - zebra: Outputs either "even" or "odd". Useful for zebra striping in
+ *   teaser listings.
+ * - id: Position of the node. Increments each time it's output.
+ *
+ * Node status variables:
+ * - view_mode: View mode; for example, "teaser" or "full".
+ * - teaser: Flag for the teaser state. Will be true if view_mode is 'teaser'.
+ * - page: Flag for the full page state. Will be true if view_mode is 'full'.
+ * - promote: Flag for front page promotion state.
+ * - sticky: Flag for sticky post setting.
+ * - status: Flag for published status.
+ * - comment: State of comment settings for the node.
+ * - readmore: Flag for more state. Will be true if the teaser content of the
+ *   node cannot hold the main body content.
+ * - is_front: Flag for front. Will be true when presented on the front page.
+ * - logged_in: Flag for authenticated user status. Will be true when the
+ *   current user is a logged-in member.
+ * - is_admin: Flag for admin user status. Will be true when the current user
+ *   is an administrator.
+ *
+ * Field variables: for each field instance attached to the node a corresponding
+ * variable is defined; for example, $node->body becomes body. When needing to
+ * access a field's raw values, developers/themers are strongly encouraged to
+ * use these variables. Otherwise they will have to explicitly specify the
+ * desired field language; for example, $node->body['en'], thus overriding any
+ * language negotiation rule that was previously applied.
+ *
+ * @see template_preprocess()
+ * @see template_preprocess_node()
+ *
+ * @ingroup themeable
+ */
+#}
+<article id="node-{{ node.nid }}" class="{{ attributes.class }} clearfix"{{ attributes }}>
+
+  {{ title_prefix }}
+  {% if not page %}
+    <h2{{ title_attributes }}>
+      <a href="{{ node_url }}" rel="bookmark">{{ label }}</a>
+    </h2>
+  {% endif %}
+  {{ title_suffix }}
+
+  {% if display_submitted %}
+    <footer>
+      {{ user_picture }}
+      <p class="submitted">{{ submitted }}</p>
+    </footer>
+  {% endif %}
+
+  <div class="content"{{ content_attributes }}>
+    {# We hide the comments and links now so that we can render them later. #}
+    {% hide(content.comments) %}
+    {% hide(content.links) %}
+    {{ content }}
+  </div>
+
+  {{ content.links }}
+  {{ content.comments }}
+
+</article>
diff --git a/core/modules/overlay/overlay-child-rtl.css b/core/modules/overlay/overlay-child-rtl.css
index 0c5edcb..eeff66c 100644
--- a/core/modules/overlay/overlay-child-rtl.css
+++ b/core/modules/overlay/overlay-child-rtl.css
@@ -33,6 +33,3 @@ html {
   left: 20px;
   right: auto;
 }
-#overlay-tabs li {
-  margin: 0 -3px 0 0;
-}
diff --git a/core/modules/overlay/overlay-child.css b/core/modules/overlay/overlay-child.css
index 7afbe25..48f217d 100644
--- a/core/modules/overlay/overlay-child.css
+++ b/core/modules/overlay/overlay-child.css
@@ -83,16 +83,16 @@
  * Tabs on the overlay.
  */
 #overlay-tabs {
-  line-height: 27px;
+  line-height: 26px;
   margin: -28px 0 0 0;
   position: absolute;
   right: 20px; /* LTR */
   text-transform: uppercase;
 }
 #overlay-tabs li {
-  display: inline;
+  display: inline-block;
   list-style: none;
-  margin: 0 0 0 -3px; /* LTR */
+  margin: 0;
   padding: 0;
 }
 #overlay-tabs li a,
@@ -105,7 +105,7 @@
   display: inline-block;
   font-size: 11px;
   font-weight: bold;
-  margin: 0 0 2px 0;
+  margin: 0 1px;
   outline: 0;
   padding: 0 14px;
   text-decoration: none;
@@ -115,7 +115,7 @@
 #overlay-tabs li.active a:active,
 #overlay-tabs li.active a:visited {
   background-color: #fff;
-  margin: 0;
+  margin-bottom: 0;
   padding-bottom: 2px;
 }
 #overlay-tabs li a:focus,
diff --git a/core/modules/picture/lib/Drupal/picture/PictureMappingFormController.php b/core/modules/picture/lib/Drupal/picture/PictureMappingFormController.php
new file mode 100644
index 0000000..3feaf5d
--- /dev/null
+++ b/core/modules/picture/lib/Drupal/picture/PictureMappingFormController.php
@@ -0,0 +1,147 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\picture\PictureFormController.
+ */
+
+namespace Drupal\picture;
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Entity\EntityFormController;
+use Drupal\picture\PictureMapping;
+
+/**
+ * Form controller for the picture edit/add forms.
+ */
+class PictureMappingFormController extends EntityFormController {
+
+  /**
+   * Overrides Drupal\Core\Entity\EntityFormController::form().
+   *
+   * @param array $form
+   *   A nested array form elements comprising the form.
+   * @param array $form_state
+   *   An associative array containing the current state of the form.
+   * @param \Drupal\picture\PictureMapping $picture_mapping
+   *   The entity being edited.
+   *
+   * @return array
+   *   The array containing the complete form.
+   */
+  public function form(array $form, array &$form_state, EntityInterface $picture_mapping) {
+    $form['label'] = array(
+      '#type' => 'textfield',
+      '#title' => t('Label'),
+      '#maxlength' => 255,
+      '#default_value' => $picture_mapping->label(),
+      '#description' => t("Example: 'Hero image' or 'Author image'."),
+      '#required' => TRUE,
+    );
+    $form['id'] = array(
+      '#type' => 'machine_name',
+      '#default_value' => $picture_mapping->id(),
+      '#machine_name' => array(
+        'exists' => 'picture_mapping_load',
+        'source' => array('label'),
+      ),
+      '#disabled' => (bool) $picture_mapping->id() && $this->operation != 'duplicate',
+    );
+
+    if ((bool) $picture_mapping->id() && $this->operation != 'duplicate') {
+      $description = t('Select a breakpoint group from the enabled themes.') . ' ' . t("Warning: if you change the breakpoint group you lose all you're selected mappings.");
+    }
+    else {
+      $description = t('Select a breakpoint group from the enabled themes.');
+    }
+    $form['breakpointGroup'] = array(
+      '#type' => 'select',
+      '#title' => t('Breakpoint Group'),
+      '#default_value' => !empty($picture_mapping->breakpointGroup) ? $picture_mapping->breakpointGroup->id() : '',
+      '#options' => breakpoint_group_select_options(),
+      '#required' => TRUE,
+      '#description' => $description,
+    );
+
+    $image_styles = image_style_options(TRUE);
+    foreach ($picture_mapping->mappings as $breakpoint_id => $mapping) {
+      foreach ($mapping as $multiplier => $image_style) {
+        $label = $multiplier . ' ' . $picture_mapping->breakpointGroup->breakpoints[$breakpoint_id]->name . ' [' . $picture_mapping->breakpointGroup->breakpoints[$breakpoint_id]->mediaQuery . ']';
+        $form['mappings'][$breakpoint_id][$multiplier] = array(
+          '#type' => 'select',
+          '#title' => check_plain($label),
+          '#options' => $image_styles,
+          '#default_value' => $image_style,
+          '#description' => t('Select an image style for this breakpoint.'),
+        );
+      }
+    }
+
+    $form['#tree'] = TRUE;
+
+    return parent::form($form, $form_state, $picture_mapping);
+  }
+
+  /**
+   * Overrides Drupal\Core\Entity\EntityFormController::actions().
+   */
+  protected function actions(array $form, array &$form_state) {
+    // Only includes a Save action for the entity, no direct Delete button.
+    return array(
+      'submit' => array(
+        '#value' => t('Save'),
+        '#validate' => array(
+          array($this, 'validate'),
+        ),
+        '#submit' => array(
+          array($this, 'submit'),
+          array($this, 'save'),
+        ),
+      ),
+    );
+  }
+
+  /**
+   * Overrides Drupal\Core\Entity\EntityFormController::validate().
+   */
+  public function validate(array $form, array &$form_state) {
+    $picture_mapping = $this->getEntity($form_state);
+
+    // Only validate on edit.
+    if (isset($form_state['values']['mappings'])) {
+      $picture_mapping->mappings = $form_state['values']['mappings'];
+
+      // Check if another breakpoint group is selected.
+      if ($form_state['values']['breakpointGroup'] != $form_state['complete_form']['breakpointGroup']['#default_value']) {
+        // Remove the mappings.
+        unset($form_state['values']['mappings']);
+      }
+      // Make sure at least one mapping is defined.
+      elseif (!$picture_mapping->isNew() && !$picture_mapping->hasMappings()) {
+        form_set_error('mappings', t('Please select at least one mapping.'));
+      }
+    }
+  }
+
+  /**
+   * Overrides Drupal\Core\Entity\EntityFormController::save().
+   */
+  public function save(array $form, array &$form_state) {
+    $picture_mapping = $this->getEntity($form_state);
+    $picture_mapping->save();
+
+    watchdog('picture', 'Picture mapping @label saved.', array('@label' => $picture_mapping->label()), WATCHDOG_NOTICE);
+    drupal_set_message(t('Picture mapping %label saved.', array('%label' => $picture_mapping->label())));
+
+    // Redirect to edit form after creating a new mapping or after selecting
+    // another breakpoint group.
+    if (!$picture_mapping->hasMappings()) {
+      $uri = $picture_mapping->uri();
+      $form_state['redirect'] = $uri['path'] . '/edit';
+    }
+    else {
+      $form_state['redirect'] = 'admin/config/media/picturemapping';
+    }
+  }
+
+}
diff --git a/core/modules/picture/lib/Drupal/picture/PictureMappingListController.php b/core/modules/picture/lib/Drupal/picture/PictureMappingListController.php
new file mode 100644
index 0000000..f63127d
--- /dev/null
+++ b/core/modules/picture/lib/Drupal/picture/PictureMappingListController.php
@@ -0,0 +1,50 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\picture\PictureListController.
+ */
+
+namespace Drupal\picture;
+
+use Drupal\Core\Config\Entity\ConfigEntityListController;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\picture\PictureMapping;
+
+/**
+ * Provides a listing of Pictures.
+ */
+class PictureMappingListController extends ConfigEntityListController {
+
+  /**
+   * Overrides Drupal\config\EntityListControllerBase::hookMenu().
+   */
+  public function hookMenu() {
+    $path = $this->entityInfo['list path'];
+    $items = parent::hookMenu();
+
+    // Override the access callback.
+    $items[$path]['title'] = 'Picture Mappings';
+    $items[$path]['description'] = 'Manage list of picture mappings.';
+    $items[$path]['access callback'] = 'user_access';
+    $items[$path]['access arguments'] = array('administer pictures');
+
+    return $items;
+  }
+
+  /**
+   * Overrides Drupal\config\ConfigEntityListController::getOperations();
+   */
+  public function getOperations(EntityInterface $entity) {
+    $operations = parent::getOperations($entity);
+    $uri = $entity->uri();
+    $operations['duplicate'] = array(
+      'title' => t('Duplicate'),
+      'href' => $uri['path'] . '/duplicate',
+      'options' => $uri['options'],
+      'weight' => 15,
+    );
+    return $operations;
+  }
+
+}
diff --git a/core/modules/picture/lib/Drupal/picture/Plugin/Core/Entity/PictureMapping.php b/core/modules/picture/lib/Drupal/picture/Plugin/Core/Entity/PictureMapping.php
new file mode 100644
index 0000000..b44d8bf
--- /dev/null
+++ b/core/modules/picture/lib/Drupal/picture/Plugin/Core/Entity/PictureMapping.php
@@ -0,0 +1,161 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\picture\PictureMapping.
+ */
+
+namespace Drupal\picture\Plugin\Core\Entity;
+
+use Drupal\Core\Config\Entity\ConfigEntityBase;
+use Drupal\Core\Annotation\Plugin;
+use Drupal\Core\Annotation\Translation;
+
+/**
+ * Defines the Picture entity.
+ * 
+ * @Plugin(
+ *   id = "picture_mapping",
+ *   label = @Translation("Picture mapping"),
+ *   module = "picture",
+ *   controller_class = "Drupal\Core\Config\Entity\ConfigStorageController",
+ *   form_controller_class = {
+ *     "default" = "Drupal\picture\PictureMappingFormController",
+ *     "add" = "Drupal\picture\PictureMappingFormController",
+ *     "duplicate" = "Drupal\picture\PictureMappingFormController"
+ *   },
+ *   list_controller_class = "Drupal\picture\PictureMappingListController",
+ *   list_path = "admin/config/media/picturemapping",
+ *   uri_callback = "picture_mapping_uri",
+ *   config_prefix = "picture.mappings",
+ *   entity_keys = {
+ *     "id" = "id",
+ *     "label" = "label",
+ *     "uuid" = "uuid"
+ *   }
+ * )
+ */
+class PictureMapping extends ConfigEntityBase {
+
+  /**
+   * The picture ID (machine name).
+   *
+   * @var string
+   */
+  public $id;
+
+  /**
+   * The picture UUID.
+   *
+   * @var string
+   */
+  public $uuid;
+
+  /**
+   * The picture label.
+   *
+   * @var string
+   */
+  public $label;
+
+  /**
+   * The picture mappings.
+   *
+   * @var array
+   */
+  public $mappings = array();
+
+  /**
+   * The picture breakpoint group.
+   *
+   * @var BreakpointGroup
+   */
+  public $breakpointGroup = '';
+
+  /**
+   * Overrides Drupal\config\ConfigEntityBase::__construct().
+   */
+  public function __construct(array $values, $entity_type) {
+    parent::__construct($values, $entity_type);
+    $this->loadBreakpointGroup();
+    $this->loadAllMappings();
+  }
+
+  /**
+   * Overrides Drupal\Core\Entity::save().
+   */
+  public function save() {
+    // Only save the keys, but return the full objects.
+    if (isset($this->breakpointGroup) && is_object($this->breakpointGroup)) {
+      $this->breakpointGroup = $this->breakpointGroup->id();
+    }
+    parent::save();
+    $this->loadBreakpointGroup();
+    $this->loadAllMappings();
+  }
+
+  /**
+   * Implements EntityInterface::createDuplicate().
+   */
+  public function createDuplicate() {
+    return entity_create('picture_mapping', array(
+      'id' => '',
+      'label' => t('Clone of !label', array('!label' => check_plain($this->label()))),
+      'mappings' => $this->mappings,
+    ));
+  }
+
+  /**
+   * Load breakpoint group.
+   */
+  protected function loadBreakpointGroup() {
+    if ($this->breakpointGroup) {
+      $breakpoint_group = entity_load('breakpoint_group', $this->breakpointGroup);
+      $this->breakpointGroup = $breakpoint_group;
+    }
+  }
+
+  /**
+   * Load all mappings, remove non-existing ones.
+   */
+  protected function loadAllMappings() {
+    $loaded_mappings = $this->mappings;
+    $this->mappings = array();
+    if ($this->breakpointGroup) {
+      foreach ($this->breakpointGroup->breakpoints as $breakpoint_id => $breakpoint) {
+        // Get the mapping for the default multiplier.
+        $this->mappings[$breakpoint_id]['1x'] = '';
+        if (isset($loaded_mappings[$breakpoint_id]['1x'])) {
+          $this->mappings[$breakpoint_id]['1x'] = $loaded_mappings[$breakpoint_id]['1x'];
+        }
+
+        // Get the mapping for the other multipliers.
+        if (isset($breakpoint->multipliers) && !empty($breakpoint->multipliers)) {
+          foreach ($breakpoint->multipliers as $multiplier => $status) {
+            if ($status) {
+              $this->mappings[$breakpoint_id][$multiplier] = '';
+              if (isset($loaded_mappings[$breakpoint_id][$multiplier])) {
+                $this->mappings[$breakpoint_id][$multiplier] = $loaded_mappings[$breakpoint_id][$multiplier];
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+
+  /**
+   * Check if there's at least one mapping defined.
+   */
+  public function hasMappings() {
+    $mapping_found = FALSE;
+    foreach ($this->mappings as $breakpoint => $multipliers) {
+      $filtered_array = array_filter($multipliers);
+      if (!empty($filtered_array)) {
+        $mapping_found = TRUE;
+        break;
+      }
+    }
+    return $mapping_found;
+  }
+}
diff --git a/core/modules/picture/lib/Drupal/picture/Plugin/field/formatter/PictureFormatter.php b/core/modules/picture/lib/Drupal/picture/Plugin/field/formatter/PictureFormatter.php
new file mode 100644
index 0000000..a4e8398
--- /dev/null
+++ b/core/modules/picture/lib/Drupal/picture/Plugin/field/formatter/PictureFormatter.php
@@ -0,0 +1,189 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\picture\Plugin\field\formatter\PictureFormatter.
+ */
+
+namespace Drupal\picture\Plugin\field\formatter;
+
+use Drupal\Core\Annotation\Plugin;
+use Drupal\Core\Annotation\Translation;
+use Drupal\field\Plugin\Type\Formatter\FormatterBase;
+use Drupal\Core\Entity\EntityInterface;
+
+/**
+ * Plugin for picture formatter.
+ *
+ * @Plugin(
+ *   id = "picture",
+ *   module = "picture",
+ *   label = @Translation("Picture"),
+ *   field_types = {
+ *     "image",
+ *   },
+ *   settings = {
+ *     "picture_mapping" = "",
+ *     "fallback_image_style" = "",
+ *     "image_link" = "",
+ *   }
+ * )
+ */
+class PictureFormatter extends FormatterBase {
+
+  /**
+   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   */
+  public function settingsForm(array $form, array &$form_state) {
+    $picture_options = array();
+    $picture_mappings = entity_load_multiple('picture_mapping');
+    if ($picture_mappings && !empty($picture_mappings)) {
+      foreach ($picture_mappings as $machine_name => $picture_mapping) {
+        if ($picture_mapping->hasMappings()) {
+          $picture_options[$machine_name] = $picture_mapping->label();
+        }
+      }
+    }
+
+    $elements['picture_mapping'] = array(
+      '#title' => t('Picture mapping'),
+      '#type' => 'select',
+      '#default_value' => $this->getSetting('picture_mapping'),
+      '#required' => TRUE,
+      '#options' => $picture_options,
+    );
+
+    $image_styles = image_style_options(FALSE);
+    $elements['fallback_image_style'] = array(
+      '#title' => t('Fallback image style'),
+      '#type' => 'select',
+      '#default_value' => $this->getSetting('fallback_image_style'),
+      '#empty_option' => t('Automatic'),
+      '#options' => $image_styles,
+    );
+
+    $link_types = array(
+      'content' => t('Content'),
+      'file' => t('File'),
+    );
+    $elements['image_link'] = array(
+      '#title' => t('Link image to'),
+      '#type' => 'select',
+      '#default_value' => $this->getSetting('image_link'),
+      '#empty_option' => t('Nothing'),
+      '#options' => $link_types,
+    );
+
+    return $elements;
+  }
+
+  /**
+   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::settingsForm().
+   */
+  public function settingsSummary() {
+    $summary = array();
+
+    $picture_mapping = entity_load('picture_mapping', $this->getSetting('picture_mapping'));
+    if ($picture_mapping) {
+      $summary[] = t('Picture mapping: @picture_mapping', array('@picture_mapping' => $picture_mapping->label()));
+
+      $image_styles = image_style_options(FALSE);
+      unset($image_styles['']);
+      if (isset($image_styles[$this->getSetting('fallback_image_style')])) {
+        $summary[] = t('Fallback Image style: @style', array('@style' => $image_styles[$this->getSetting('fallback_image_style')]));
+      }
+      else {
+        $summary[] = t('Automatic fallback');
+      }
+
+      $link_types = array(
+        'content' => t('Linked to content'),
+        'file' => t('Linked to file'),
+      );
+      // Display this setting only if image is linked.
+      if (isset($link_types[$this->getSetting('image_link')])) {
+        $summary[] = $link_types[$this->getSetting('image_link')];
+      }
+    }
+    else {
+      $summary[] = t('Please select a picture mapping');
+    }
+
+    return implode('<br />', $summary);
+  }
+
+  /**
+   * Implements Drupal\field\Plugin\Type\Formatter\FormatterInterface::viewElements().
+   */
+  public function viewElements(EntityInterface $entity, $langcode, array $items) {
+    $elements = array();
+    // Check if the formatter involves a link.
+    if ($this->getSetting('image_link') == 'content') {
+      $uri = $entity->uri();
+    }
+    elseif ($this->getSetting('image_link') == 'file') {
+      $link_file = TRUE;
+    }
+
+    $breakpoint_styles = array();
+    $fallback_image_style = '';
+
+    $picture_mapping = entity_load('picture_mapping', $this->getSetting('picture_mapping'));
+    if ($picture_mapping) {
+      foreach ($picture_mapping->mappings as $breakpoint_name => $multipliers) {
+        // Make sure there are multipliers.
+        if (!empty($multipliers)) {
+          // Make sure that the breakpoint exists and is enabled.
+          // @todo add the following when breakpoint->status is added again:
+          // $picture_mapping->breakpointGroup->breakpoints[$breakpoint_name]->status
+          if (isset($picture_mapping->breakpointGroup->breakpoints[$breakpoint_name])) {
+          $breakpoint = $picture_mapping->breakpointGroup->breakpoints[$breakpoint_name];
+
+          // Determine the enabled multipliers.
+          $multipliers = array_intersect_key($multipliers, $breakpoint->multipliers);
+            foreach ($multipliers as $multiplier => $image_style) {
+              // Make sure the multiplier still exists.
+              //if (!empty(array_intersect($multiplier, $breakpoint->multipliers))) {
+              if (!empty($image_style)) {
+                // First mapping found is used as fallback.
+                if (empty($fallback_image_style)) {
+                  $fallback_image_style = $image_style;
+                }
+                if (!isset($breakpoint_styles[$breakpoint_name])) {
+                  $breakpoint_styles[$breakpoint_name] = array();
+                }
+                $breakpoint_styles[$breakpoint_name][$multiplier] = $image_style;
+              }
+            }
+          }
+        }
+      }
+    }
+
+    // Check if the user defined a custom fallback image style.
+    if ($this->getSetting('fallback_image_style')) {
+      $fallback_image_style = $this->getSetting('fallback_image_style');
+    }
+
+    foreach ($items as $delta => $item) {
+      if (isset($link_file)) {
+        $uri = array(
+          'path' => file_create_url($item['uri']),
+          'options' => array(),
+        );
+      }
+      $elements[$delta] = array(
+        '#theme' => 'picture_formatter',
+        '#attached' => array('library' => array(
+          array('picture', 'picturefill'),
+        )),
+        '#item' => $item,
+        '#image_style' => $fallback_image_style,
+        '#breakpoints' => $breakpoint_styles,
+        '#path' => isset($uri) ? $uri : '',
+      );
+    }
+
+    return $elements;
+  }
+}
diff --git a/core/modules/picture/lib/Drupal/picture/Tests/PictureAdminUITest.php b/core/modules/picture/lib/Drupal/picture/Tests/PictureAdminUITest.php
new file mode 100644
index 0000000..114e30c
--- /dev/null
+++ b/core/modules/picture/lib/Drupal/picture/Tests/PictureAdminUITest.php
@@ -0,0 +1,141 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\picture\Tests\PictureAdminUITest.
+ */
+
+namespace Drupal\picture\Tests;
+
+use Drupal\simpletest\WebTestBase;
+use Drupal\breakpoint\Plugin\Core\Entity\Breakpoint;
+
+/**
+ * Tests for breakpoint sets admin interface.
+ */
+class PictureAdminUITest extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('picture');
+
+  /**
+   * Drupal\simpletest\WebTestBase\getInfo().
+   */
+  public static function getInfo() {
+    return array(
+      'name' => 'Picture administration functionality',
+      'description' => 'Thoroughly test the administrative interface of the picture module.',
+      'group' => 'Picture',
+    );
+  }
+
+  /**
+   * Drupal\simpletest\WebTestBase\setUp().
+   */
+  public function setUp() {
+    parent::setUp();
+
+    // Create user.
+    $this->admin_user = $this->drupalCreateUser(array(
+      'administer pictures',
+    ));
+
+    $this->drupalLogin($this->admin_user);
+
+    // Add breakpoint_group and breakpoints.
+    $breakpoint_group = entity_create('breakpoint_group', array(
+      'id' => 'atestset',
+      'label' => 'A test set',
+      'sourceType' => Breakpoint::SOURCE_TYPE_USER_DEFINED,
+    ));
+
+    $breakpoints = array();
+    $breakpoint_names = array('small', 'medium', 'large');
+    for ($i = 0; $i < 3; $i++) {
+      $width = ($i + 1) * 200;
+      $breakpoint = entity_create('breakpoint', array(
+        'name' => $breakpoint_names[$i],
+        'mediaQuery' => "(min-width: {$width}px)",
+        'source' => 'user',
+        'sourceType' => Breakpoint::SOURCE_TYPE_USER_DEFINED,
+        'multipliers' => array(
+          '1.5x' => 0,
+          '2x' => '2x',
+        ),
+      ));
+      $breakpoint->save();
+      $breakpoint_group->breakpoints[$breakpoint->id()] = $breakpoint;
+    }
+    $breakpoint_group->save();
+
+  }
+
+  /**
+   * Test picture administration functionality.
+   */
+  public function testPictureAdmin() {
+    // We start without any default mappings.
+    $this->drupalGet('admin/config/media/picturemapping');
+    $this->assertText('There is no Picture mapping yet.');
+
+    // Add a new picture mapping, our breakpoint set should be selected.
+    $this->drupalGet('admin/config/media/picturemapping/add');
+    $this->assertFieldByName('breakpointGroup', 'atestset');
+
+    // Create a new group.
+    $edit = array(
+      'label' => 'Mapping One',
+      'id' => 'mapping_one',
+      'breakpointGroup' => 'atestset',
+    );
+    $this->drupalPost('admin/config/media/picturemapping/add', $edit, t('Save'));
+
+    // Check if the new group is created.
+    $this->assertResponse(200);
+    $this->drupalGet('admin/config/media/picturemapping');
+    $this->assertNoText('There is no Picture mapping yet.');
+    $this->assertText('Mapping One');
+    $this->assertText('mapping_one');
+
+    // Edit the group.
+    $this->drupalGet('admin/config/media/picturemapping/mapping_one/edit');
+    $this->assertFieldByName('label', 'Mapping One');
+    $this->assertFieldByName('breakpointGroup', 'atestset');
+
+    // Check if the dropdows are present for the mappings.
+    $this->assertFieldByName('mappings[custom.user.small][1x]', '');
+    $this->assertFieldByName('mappings[custom.user.small][2x]', '');
+    $this->assertFieldByName('mappings[custom.user.medium][1x]', '');
+    $this->assertFieldByName('mappings[custom.user.medium][2x]', '');
+    $this->assertFieldByName('mappings[custom.user.large][1x]', '');
+    $this->assertFieldByName('mappings[custom.user.large][2x]', '');
+
+    // Save mappings for 1x variant only.
+    $edit = array(
+      'label' => 'Mapping One',
+      'breakpointGroup' => 'atestset',
+      'mappings[custom.user.small][1x]' => 'thumbnail',
+      'mappings[custom.user.medium][1x]' => 'medium',
+      'mappings[custom.user.large][1x]' => 'large',
+    );
+    $this->drupalPost('admin/config/media/picturemapping/mapping_one/edit', $edit, t('Save'));
+    $this->drupalGet('admin/config/media/picturemapping/mapping_one/edit');
+    $this->assertFieldByName('mappings[custom.user.small][1x]', 'thumbnail');
+    $this->assertFieldByName('mappings[custom.user.small][2x]', '');
+    $this->assertFieldByName('mappings[custom.user.medium][1x]', 'medium');
+    $this->assertFieldByName('mappings[custom.user.medium][2x]', '');
+    $this->assertFieldByName('mappings[custom.user.large][1x]', 'large');
+    $this->assertFieldByName('mappings[custom.user.large][2x]', '');
+
+    // Delete the mapping.
+    $this->drupalGet('admin/config/media/picturemapping/mapping_one/delete');
+    $this->drupalPost(NULL, array(), t('Delete'));
+    $this->drupalGet('admin/config/media/picturemapping');
+    $this->assertText('There is no Picture mapping yet.');
+  }
+
+}
diff --git a/core/modules/picture/lib/Drupal/picture/Tests/PictureFieldDisplayTest.php b/core/modules/picture/lib/Drupal/picture/Tests/PictureFieldDisplayTest.php
new file mode 100644
index 0000000..69b0231
--- /dev/null
+++ b/core/modules/picture/lib/Drupal/picture/Tests/PictureFieldDisplayTest.php
@@ -0,0 +1,199 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\picture\Tests\PictureFieldDisplayTest.
+ */
+
+namespace Drupal\picture\Tests;
+
+use Drupal\breakpoint\Plugin\Core\Entity\Breakpoint;
+use Drupal\image\Tests\ImageFieldTestBase;
+
+/**
+ * Test class to check that formatters and display settings are working.
+ */
+class PictureFieldDisplayTest extends ImageFieldTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('field_ui', 'picture');
+
+  /**
+   * Drupal\simpletest\WebTestBase\getInfo().
+   */
+  public static function getInfo() {
+    return array(
+      'name' => 'Picture field display tests',
+      'description' => 'Test picture display formatter.',
+      'group' => 'Picture',
+    );
+  }
+
+  /**
+   * Drupal\simpletest\WebTestBase\setUp().
+   */
+  public function setUp() {
+    parent::setUp();
+
+    // Create user.
+    $this->admin_user = $this->drupalCreateUser(array(
+      'administer pictures',
+      'access content',
+      'access administration pages',
+      'administer site configuration',
+      'administer content types',
+      'administer nodes',
+      'create article content',
+      'edit any article content',
+      'delete any article content',
+      'administer image styles'
+    ));
+    $this->drupalLogin($this->admin_user);
+
+    // Add breakpoint_group and breakpoints.
+    $breakpoint_group = entity_create('breakpoint_group', array(
+      'id' => 'atestset',
+      'label' => 'A test set',
+      'sourceType' => Breakpoint::SOURCE_TYPE_USER_DEFINED,
+    ));
+
+    $breakpoints = array();
+    $breakpoint_names = array('small', 'medium', 'large');
+    for ($i = 0; $i < 3; $i++) {
+      $width = ($i + 1) * 200;
+      $breakpoint = entity_create('breakpoint', array(
+        'name' => $breakpoint_names[$i],
+        'mediaQuery' => "(min-width: {$width}px)",
+        'source' => 'user',
+        'sourceType' => Breakpoint::SOURCE_TYPE_USER_DEFINED,
+        'multipliers' => array(
+          '1.5x' => 0,
+          '2x' => '2x',
+        ),
+      ));
+      $breakpoint->save();
+      $breakpoint_group->breakpoints[$breakpoint->id()] = $breakpoint;
+    }
+    $breakpoint_group->save();
+
+    // Add picture mapping.
+    $picture_mapping = entity_create('picture_mapping', array(
+      'id' => 'mapping_one',
+      'label' => 'Mapping One',
+      'breakpointGroup' => 'atestset',
+    ));
+    $picture_mapping->save();
+    $picture_mapping->mappings['custom.user.small']['1x'] = 'thumbnail';
+    $picture_mapping->mappings['custom.user.medium']['1x'] = 'medium';
+    $picture_mapping->mappings['custom.user.large']['1x'] = 'large';
+    $picture_mapping->save();
+  }
+
+  /**
+   * Test picture formatters on node display for public files.
+   */
+  public function testPictureFieldFormattersPublic() {
+    $this->_testPictureFieldFormatters('public');
+  }
+
+  /**
+   * Test picture formatters on node display for private files.
+   */
+  public function testPictureFieldFormattersPrivate() {
+    // Remove access content permission from anonymous users.
+    user_role_change_permissions(DRUPAL_ANONYMOUS_RID, array('access content' => FALSE));
+    $this->_testPictureFieldFormatters('private');
+  }
+
+  /**
+   * Test picture formatters on node display.
+   */
+  public function _testPictureFieldFormatters($scheme) {
+    $field_name = drupal_strtolower($this->randomName());
+    $this->createImageField($field_name, 'article', array('uri_scheme' => $scheme));
+    // Create a new node with an image attached.
+    $test_image = current($this->drupalGetTestFiles('image'));
+    $nid = $this->uploadNodeImage($test_image, $field_name, 'article');
+    $node = node_load($nid, TRUE);
+
+    // Use the picture formatter.
+    $instance = field_info_instance('node', $field_name, 'article');
+    $instance['display']['default']['type'] = 'picture';
+    $instance['display']['default']['module'] = 'picture';
+
+    // Test that the default formatter is being used.
+    $image_uri = file_load($node->{$field_name}[LANGUAGE_NOT_SPECIFIED][0]['fid'])->uri;
+    $image_info = array(
+      'uri' => $image_uri,
+      'width' => 40,
+      'height' => 20,
+    );
+    $default_output = theme('image', $image_info);
+    $this->assertRaw($default_output, 'Default formatter displaying correctly on full node view.');
+
+    // Use the picture formatter linked to file formatter.
+    $instance = field_info_instance('node', $field_name, 'article');
+    $instance['display']['default']['type'] = 'picture';
+    $instance['display']['default']['module'] = 'picture';
+    $instance['display']['default']['settings']['image_link'] = 'file';
+    field_update_instance($instance);
+    $default_output = l(theme('image', $image_info), file_create_url($image_uri), array('html' => TRUE));
+    $this->drupalGet('node/' . $nid);
+    $this->assertRaw($default_output, 'Image linked to file formatter displaying correctly on full node view.');
+    // Verify that the image can be downloaded.
+    $this->assertEqual(file_get_contents($test_image->uri), $this->drupalGet(file_create_url($image_uri)), 'File was downloaded successfully.');
+    if ($scheme == 'private') {
+      // Only verify HTTP headers when using private scheme and the headers are
+      // sent by Drupal.
+      $this->assertEqual($this->drupalGetHeader('Content-Type'), 'image/png', 'Content-Type header was sent.');
+      $this->assertEqual($this->drupalGetHeader('Content-Disposition'), 'inline; filename="' . $test_image->filename . '"', 'Content-Disposition header was sent.');
+      $this->assertTrue(strstr($this->drupalGetHeader('Cache-Control'), 'private') !== FALSE, 'Cache-Control header was sent.');
+
+      // Log out and try to access the file.
+      $this->drupalLogout();
+      $this->drupalGet(file_create_url($image_uri));
+      $this->assertResponse('403', 'Access denied to original image as anonymous user.');
+
+      // Log in again.
+      $this->drupalLogin($this->admin_user);
+    }
+
+    // Use the picture formatter with a picture mapping.
+    $instance['display']['default']['settings']['picture_mapping'] = 'mapping_one';
+    field_update_instance($instance);
+    // Output should contain all image styles and all breakpoints.
+    $this->drupalGet('node/' . $nid);
+    $this->assertRaw('/styles/thumbnail/');
+    $this->assertRaw('/styles/medium/');
+    $this->assertRaw('/styles/large/');
+    $this->assertRaw('media="(min-width: 200px)"');
+    $this->assertRaw('media="(min-width: 400px)"');
+    $this->assertRaw('media="(min-width: 600px)"');
+
+    // Test the fallback image style.
+    $instance['display']['default']['settings']['image_link'] = '';
+    $instance['display']['default']['settings']['fallback_image_style'] = 'large';
+    field_update_instance($instance);
+
+    $this->drupalGet(image_style_url('large', $image_uri));
+    $image_info['uri'] = $image_uri;
+    $image_info['width'] = 480;
+    $image_info['height'] = 240;
+    $image_info['style_name'] = 'large';
+    $default_output = '<noscript>' . theme('image_style', $image_info) . '</noscript>';
+    $this->drupalGet('node/' . $nid);
+    $this->assertRaw($default_output, 'Image style thumbnail formatter displaying correctly on full node view.');
+
+    if ($scheme == 'private') {
+      // Log out and try to access the file.
+      $this->drupalLogout();
+      $this->drupalGet(image_style_url('large', $image_uri));
+      $this->assertResponse('403', 'Access denied to image style thumbnail as anonymous user.');
+    }
+  }
+
+}
diff --git a/core/modules/picture/picture.info b/core/modules/picture/picture.info
new file mode 100644
index 0000000..3113a7f
--- /dev/null
+++ b/core/modules/picture/picture.info
@@ -0,0 +1,9 @@
+name = Picture
+description = Picture element
+package = Core
+version = VERSION
+core = 8.x
+dependencies[] = breakpoint
+dependencies[] = config
+dependencies[] = image
+configure = admin/config/media/picturemapping
diff --git a/core/modules/picture/picture.module b/core/modules/picture/picture.module
new file mode 100644
index 0000000..5d77db6
--- /dev/null
+++ b/core/modules/picture/picture.module
@@ -0,0 +1,379 @@
+<?php
+
+/**
+ * @file
+ * Picture display formatter for image fields.
+ */
+
+use Drupal\picture\Plugin\Core\Entity\PictureMapping;
+use \Drupal\Core\Template\Attribute;
+
+/**
+ * Implements hook_help().
+ */
+function picture_help($path, $arg) {
+  $output = '';
+  switch ($path) {
+    case 'admin/help#picture':
+      $output .= '<h3>' . t('About') . '</h3>';
+      $output .= '<p>' . t('The picture module allows you to output responsive images using the new <a href="@link">HTML5 picture tag</a>.', array(
+        '@link' => 'http://responsiveimages.org/',
+      )) . '</p>';
+      break;
+    case 'admin/config/media/picturemapping':
+      $output .= '<p>' . t('A picture mapping associates an image style with each breakpoint defined by your theme.') . '</p>';
+      break;
+    case 'admin/config/media/picturemapping/add':
+      $output .= '<p>' . t('Create a new picture mapping by specifying a name and selecting a breakpoint group.') . '</p>';
+      break;
+    case 'admin/config/media/picturemapping/%/edit':
+      $output .= '<p>' . t('For each breakpoint you can select a corresponding image style.') . '</p>';
+      $output .= '<p>' . t("Warning: if you change the breakpoint group you lose all you're selected mappings.") . '</p>';
+      break;
+
+  }
+  return $output;
+}
+
+/**
+ * Implements hook_permission().
+ */
+function picture_permission() {
+  return array(
+    'administer pictures' => array(
+      'title' => t('Administer Pictures'),
+      'description' => t('Administer Pictures'),
+    ),
+  );
+}
+
+/**
+ * Implements hook_menu().
+ */
+function picture_menu() {
+  $items = array();
+
+  $items['admin/config/media/picturemapping'] = array(
+    'title' => 'Picture Mappings',
+    'description' => 'Manage picture mappings',
+    'access arguments' => array('administer pictures'),
+    'weight' => 10,
+    'page callback' => 'picture_mapping_page',
+    'file' => 'picture_mapping.admin.inc',
+  );
+  $items['admin/config/media/picturemapping/add'] = array(
+    'title' => 'Add picture mapping',
+    'page callback' => 'picture_mapping_page_add',
+    'access callback' => 'user_access',
+    'access arguments' => array('administer pictures'),
+    'type' => MENU_LOCAL_ACTION,
+    'file' => 'picture_mapping.admin.inc',
+  );
+  $items['admin/config/media/picturemapping/%picture_mapping/edit'] = array(
+    'title' => 'Edit picture mapping',
+    'page callback' => 'picture_mapping_page_edit',
+    'page arguments' => array(4),
+    'access callback' => 'user_access',
+    'access arguments' => array('administer pictures'),
+    'file' => 'picture_mapping.admin.inc',
+  );
+  $items['admin/config/media/picturemapping/%picture_mapping/duplicate'] = array(
+    'title' => 'Duplicate picture mapping',
+    'page callback' => 'picture_mapping_page_duplicate',
+    'page arguments' => array(4),
+    'access callback' => 'user_access',
+    'access arguments' => array('administer pictures'),
+    'file' => 'picture_mapping.admin.inc',
+  );
+  $items['admin/config/media/picturemapping/%picture_mapping/delete'] = array(
+    'title' => 'Delete',
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('picture_mapping_action_confirm', 4, 5),
+    'access callback' => 'user_access',
+    'access arguments' => array('administer pictures'),
+    'file' => 'picture_mapping.admin.inc',
+  );
+
+  return $items;
+}
+
+/**
+ * Implements hook_library_info().
+ */
+function picture_library_info() {
+  $libraries['picturefill'] = array(
+    'title' => t('Picturefill'),
+    'website' => 'http://drupal.org/node/1775530',
+    'version' => VERSION,
+    'js' => array(
+      drupal_get_path('module', 'picture') . '/picturefill/picturefill.js' => array('type' => 'file', 'weight' => -10, 'group' => JS_DEFAULT),
+    ),
+    'dependencies' => array(
+      array('system', 'matchmedia'),
+    ),
+  );
+  return $libraries;
+}
+
+/**
+ * Load one picture by its identifier.
+ *
+ * @param int $id
+ *   The id of the picture mapping to load.
+ *
+ * @return Drupal\picture\Picture
+ *   The entity object, or FALSE if there is no entity with the given id.
+ *
+ * @todo Needed for menu_callback
+ *
+ * @see http://drupal.org/node/1798214
+ *
+ */
+function picture_mapping_load($id) {
+  return entity_load('picture_mapping', $id);
+}
+
+/**
+ * Gets Picture uri callback.
+ */
+function picture_mapping_uri(PictureMapping $picture_mapping) {
+  return array(
+    'path' => 'admin/config/media/picturemapping/' . $picture_mapping->id(),
+  );
+}
+
+/**
+ * Sets Picture uri callback.
+ */
+function picture_mapping_set_uri(PictureMapping $picture_mapping) {
+  return array(
+    'path' => 'admin/config/media/picturemapping/' . $picture_mapping->id(),
+  );
+}
+
+/**
+ * Implements hook_theme().
+ */
+function picture_theme() {
+  return array(
+    'picture' => array(
+      'variables' => array(
+        'style_name' => NULL,
+        'path' => NULL,
+        'width' => NULL,
+        'height' => NULL,
+        'alt' => '',
+        'title' => NULL,
+        'attributes' => array(),
+        'breakpoints' => array(),
+      ),
+    ),
+    'picture_formatter' => array(
+      'variables' => array(
+        'item' => NULL,
+        'path' => NULL,
+        'image_style' => NULL,
+        'breakpoints' => array(),
+      ),
+    ),
+    'picture_source' => array(
+      'variables' => array(
+        'src' => NULL,
+        'srcset' => NULL,
+        'dimension' => NULL,
+        'media' => NULL,
+      ),
+    ),
+  );
+}
+
+/**
+ * Returns HTML for a picture field formatter.
+ *
+ * @param array $variables
+ *   An associative array containing:
+ *   - item: An array of image data.
+ *   - image_style: An optional image style.
+ *   - path: An optional array containing the link 'path' and link 'options'.
+ *   - breakpoints: An array containing breakpoints.
+ *
+ * @ingroup themeable
+ */
+function theme_picture_formatter($variables) {
+  if (!isset($variables['breakpoints']) || empty($variables['breakpoints'])) {
+    return theme('image_formatter', $variables);
+  }
+
+  $item = $variables['item'];
+
+  // Do not output an empty 'title' attribute.
+  if (isset($item['title']) && drupal_strlen($item['title']) == 0) {
+    unset($item['title']);
+  }
+
+  $item['style_name'] = $variables['image_style'];
+  $item['breakpoints'] = $variables['breakpoints'];
+
+  if (!isset($item['path']) && isset($variables['uri'])) {
+    $item['path'] = $variables['uri'];
+  }
+  $output = theme('picture', $item);
+
+  if (isset($variables['path']['path'])) {
+    $path = $variables['path']['path'];
+    $options = isset($variables['path']['options']) ? $variables['path']['options'] : array();
+    $options['html'] = TRUE;
+    $output = l($output, $path, $options);
+  }
+  return $output;
+}
+
+/**
+ * Returns HTML for a picture.
+ *
+ * @param $variables
+ *   An associative array containing:
+ *   - uri: Either the path of the image file (relative to base_path()) or a
+ *     full URL.
+ *   - width: The width of the image (if known).
+ *   - height: The height of the image (if known).
+ *   - alt: The alternative text for text-based browsers.
+ *   - breakpoints: An array containing breakpoints.
+ *
+ * @ingroup themeable
+ */
+function theme_picture($variables) {
+  // Make sure that width and height are proper values
+  // If they exists we'll output them
+  // @see http://www.w3.org/community/respimg/2012/06/18/florians-compromise/
+  if (isset($variables['width']) && empty($variables['width'])) {
+    unset($variables['width']);
+    unset($variables['height']);
+  }
+  elseif (isset($variables['height']) && empty($variables['height'])) {
+    unset($variables['width']);
+    unset($variables['height']);
+  }
+
+  $sources = array();
+  $output = array();
+
+  // Fallback image, output as source with media query.
+  $sources[] = array(
+    'src' => image_style_url($variables['style_name'], $variables['uri']),
+    'dimensions' => picture_get_image_dimensions($variables),
+  );
+
+  // All breakpoints and multipliers.
+  foreach ($variables['breakpoints'] as $breakpoint_name => $multipliers) {
+    $breakpoint = breakpoint_load($breakpoint_name);
+    if ($breakpoint) {
+      $new_sources = array();
+      foreach ($multipliers as $multiplier => $image_style) {
+        $new_source = $variables;
+        $new_source['style_name'] = $image_style;
+        $new_source['#multiplier'] = $multiplier;
+        $new_sources[] = $new_source;
+      }
+
+      // Only one image, use src.
+      if (count($new_sources) == 1) {
+        $sources[] = array(
+          'src' => image_style_url($new_sources[0]['style_name'], $new_sources[0]['uri']),
+          'dimensions' => picture_get_image_dimensions($new_sources[0]),
+          'media' => $breakpoint->mediaQuery,
+        );
+      }
+      else {
+        // Mutliple images, use srcset.
+        $srcset = array();
+        foreach ($new_sources as $new_source) {
+          $srcset[] = image_style_url($new_source['style_name'], $new_source['uri']) . ' ' . $new_source['#multiplier'];
+        }
+        $sources[] = array(
+          'srcset' => implode(', ', $srcset),
+          'dimensions' => picture_get_image_dimensions($new_sources[0]),
+          'media' => $breakpoint->mediaQuery,
+        );
+      }
+    }
+  }
+
+  if (!empty($sources)) {
+    $attributes = array();
+    foreach (array('alt', 'title') as $key) {
+      if (isset($variables[$key])) {
+        $attributes[$key] = $variables[$key];
+      }
+    }
+    $output[] = '<picture' . new Attribute($attributes) . '>';
+
+    // add source tags to the output.
+    foreach ($sources as $source) {
+      $output[] = theme('picture_source', $source);
+    }
+
+    // output the fallback image.
+    $output[] = '<noscript>' . theme('image_style', $variables) . '</noscript>';
+    $output[] = '</picture>';
+    return implode("\n", $output);
+  }
+}
+
+/**
+ * Returns HTML for a source tag.
+ *
+ * @param type $variables
+ *   An associative array containing:
+ *   - media: The media query to use.
+ *   - srcset: The srcset containing the the path of the image file or a full
+ *     URL and optionally multipliers.
+ *   - src: Either the path of the image file (relative to base_path()) or a
+ *     full URL.
+ *   - dimensions: The width and height of the image (if known).
+ *
+ * @ingroup themeable
+ */
+function theme_picture_source($variables) {
+  $output = array();
+  if (isset($variables['media']) && !empty($variables['media'])) {
+    if (!isset($variables['srcset'])) {
+      $output[] = '<!-- <source media="' . $variables['media'] . '" src="' . $variables['src'] . '" ' . new Attribute($variables['dimensions']) . ' /> -->';
+      $output[] = '<source media="' . $variables['media'] . '" src="' . $variables['src'] . '" ' . new Attribute($variables['dimensions']) . '/>';
+    }
+    elseif (!isset($variables['src'])) {
+      $output[] = '<!-- <source media="' . $variables['media'] . '" srcset="' . $variables['srcset'] . '" ' . new Attribute($variables['dimensions']) . ' /> -->';
+      $output[] = '<source media="' . $variables['media'] . '" srcset="' . $variables['srcset'] . '" ' . new Attribute($variables['dimensions']) . ' />';
+    }
+  }
+  else {
+    $output[] = '<!-- <source src="' . $variables['src'] . '" ' . new Attribute($variables['dimensions']) . ' /> -->';
+    $output[] = '<source src="' . $variables['src'] . '" ' . new Attribute($variables['dimensions']) . '/>';
+  }
+  return implode("\n", $output);
+}
+
+/**
+ * Determines the dimensions of an image.
+ *
+ * @param $variables
+ *   An associative array containing:
+ *   - style_name: The name of the style to be used to alter the original image.
+ *   - width: The width of the source image (if known).
+ *   - height: The height of the source image (if known).
+ *
+ * @return array
+ *   Dimensions to be modified - an array with components width and height, in
+ *   pixels.
+ */
+function picture_get_image_dimensions($variables) {
+  // Determine the dimensions of the styled image.
+  $dimensions = array(
+    'width' => $variables['width'],
+    'height' => $variables['height'],
+  );
+
+  image_style_transform_dimensions($variables['style_name'], $dimensions);
+
+  return $dimensions;
+}
diff --git a/core/modules/picture/picture_mapping.admin.inc b/core/modules/picture/picture_mapping.admin.inc
new file mode 100644
index 0000000..42e85b1
--- /dev/null
+++ b/core/modules/picture/picture_mapping.admin.inc
@@ -0,0 +1,108 @@
+<?php
+
+/**
+ * @file
+ * Administration functions to maintain picture mappings.
+ */
+
+use \Drupal\picture\PictureMapping;
+
+/**
+ * Page callback: Presents the picture list page.
+ *
+ * @return
+ *   A render array for a page containing a list of content.
+ *
+ * @see picture_menu()
+ */
+function picture_mapping_page() {
+  $controller = entity_list_controller('picture_mapping');
+  return $controller->render();
+}
+
+/**
+ * Page callback: Presents the picture mapping editing form.
+ *
+ * @param Drupal\picture\PictureMapping $picture_mapping
+ *
+ * @return
+ *   A render array for a page containing a list of content.
+ *
+ * @see picture_menu()
+ */
+function picture_mapping_page_edit($picture_mapping) {
+  drupal_set_title(t('<em>Edit picture mapping</em> @label', array('@label' => $picture_mapping->label())), PASS_THROUGH);
+  return entity_get_form($picture_mapping);
+}
+
+/**
+ * Page callback: Presents the picture mapping duplicate form.
+ *
+ * @param Drupal\picture\PictureMapping $picture_mapping
+ *
+ * @return
+ *   A render array for a page containing a list of content.
+ *
+ * @see picture_menu()
+ */
+function picture_mapping_page_duplicate($picture_mapping) {
+  drupal_set_title(t('<em>Duplicate picture mapping</em> @label', array('@label' => $picture_mapping->label())), PASS_THROUGH);
+  return entity_get_form($picture_mapping->createDuplicate());
+}
+
+/**
+ * Page callback: Provides the new picture mapping addition form.
+ *
+ * @return
+ *   A render array for a page containing a list of content.
+ *
+ * @see picture_menu()
+ */
+function picture_mapping_page_add() {
+  $picture_mapping = entity_create('picture_mapping', array());
+  $form = entity_get_form($picture_mapping);
+  return $form;
+}
+
+/**
+ * Page callback: Form constructor for picture action confirmation form.
+ *
+ * @param Drupal\picture\PictureMapping $picture_mapping
+ * @param string $action
+ *
+ * @see picture_menu()
+ */
+function picture_mapping_action_confirm($form, &$form_state, $picture_mapping, $action) {
+  // Always provide entity id in the same form key as in the entity edit form.
+  if (in_array($action, array('delete'))) {
+    $form['id'] = array('#type' => 'value', '#value' => $picture_mapping->id());
+    $form['action'] = array('#type' => 'value', '#value' => $action);
+    $form_state['picture_mapping'] = $picture_mapping;
+    $form = confirm_form($form,
+      t('Are you sure you want to @action the picture_mapping %title?', array('@action' => $action, '%title' => $picture_mapping->label())),
+      'admin/config/media/picturemapping',
+      $action == 'delete' ? t('This action cannot be undone.') : '',
+      t(drupal_ucfirst($action)),
+      t('Cancel')
+    );
+  }
+  return $form;
+}
+
+/**
+ * Form submission handler for picture_action_confirm().
+ */
+function picture_mapping_action_confirm_submit($form, &$form_state) {
+  $picture_mapping = $form_state['picture_mapping'];
+  $action = $form_state['values']['action'];
+  $picture_mapping->{$action}();
+  $verb = '';
+  switch ($action) {
+    case 'delete':
+      $verb = 'deleted';
+      break;
+  }
+  drupal_set_message(t('Picture mapping %label has been @action.', array('%label' => $picture_mapping->label(), '@action' => $verb)));
+  watchdog('picture', 'Picture mapping %label has been @action.', array('%label' => $picture_mapping->label(), '@action' => $verb), WATCHDOG_NOTICE);
+  $form_state['redirect'] = 'admin/config/media/picturemapping';
+}
diff --git a/core/modules/picture/picturefill/picturefill.js b/core/modules/picture/picturefill/picturefill.js
new file mode 100644
index 0000000..8e4c231
--- /dev/null
+++ b/core/modules/picture/picturefill/picturefill.js
@@ -0,0 +1,126 @@
+/*jshint loopfunc: true, browser: true, curly: true, eqeqeq: true, expr: true, forin: true, latedef: true, newcap: true, noarg: true, trailing: true, undef: true, unused: true */
+/*! Picturefill - Author: Scott Jehl, 2012 | License: MIT/GPLv2 */
+(function( w ){
+
+  // Enable strict mode.
+  "use strict";
+
+  // Test if `<picture>` is supported natively, if so, exit.
+  if (!!(w.document.createElement('picture') && w.document.createElement('source') && w.HTMLPictureElement)) {
+    return;
+  }
+
+  w.picturefill = function() {
+    // Copy attributes from the source to the destination.
+    function _copyAttributes(src, tar) {
+      if (src.getAttribute('width') && src.getAttribute('height')) {
+        tar.width = src.getAttribute('width');
+        tar.height = src.getAttribute('height');
+      }
+    }
+
+    // Get all picture tags.
+    var ps = w.document.getElementsByTagName('picture');
+
+    // Loop the pictures.
+    for (var i = 0, il = ps.length; i < il; i++ ) {
+      var sources = ps[i].getElementsByTagName('source');
+      var picImg = null;
+      var matches = [];
+
+      // If no sources are found, they're likely erased from the DOM.
+      // Try finding them inside comments.
+      if (!sources.length) {
+        var picText = ps[i].innerHTML;
+        var frag = w.document.createElement('div');
+        // For IE9, convert the source elements to divs.
+        var srcs = picText.replace(/(<)source([^>]+>)/gmi, '$1div$2').match(/<div[^>]+>/gmi);
+
+        frag.innerHTML = srcs.join('');
+        sources = frag.getElementsByTagName('div');
+      }
+
+      // See which sources match.
+      for (var j = 0, jl = sources.length; j < jl; j++ ) {
+        var media = sources[j].getAttribute('media');
+        // if there's no media specified, OR w.matchMedia is supported
+        if (!media || (w.matchMedia && w.matchMedia(media).matches)) {
+          matches.push(sources[j]);
+        }
+      }
+
+      if (matches.length) {
+        // Grab the most appropriate (last) match.
+        var match = matches.pop();
+        var srcset = match.getAttribute('srcset');
+
+        // Find any existing img element in the picture element.
+        picImg = ps[i].getElementsByTagName('img')[0];
+
+        // Add a new img element if one doesn't exists.
+        if (!picImg) {
+          picImg = w.document.createElement('img');
+          picImg.alt = ps[i].getAttribute('alt');
+          ps[i].appendChild(picImg);
+        }
+
+        // Source element uses a srcset.
+        if (srcset) {
+          var screenRes = w.devicePixelRatio || 1;
+          // Split comma-separated `srcset` sources into an array.
+          sources = srcset.split(', ');
+
+          // Loop through each source/resolution in srcset.
+          for (var res = sources.length, r = res - 1; r >= 0; r-- ) {
+            // Remove any leading whitespace, then split on spaces.
+            var source = sources[ r ].replace(/^\s*/, '').replace(/\s*$/, '').split(' ');
+            // Parse out the resolution for each source in `srcset`.
+            var resMatch = parseFloat(source[1], 10);
+
+            if (screenRes >= resMatch) {
+              if (picImg.getAttribute('src') !== source[0]) {
+                var newImg = document.createElement('img');
+
+                newImg.src = source[0];
+                // When the image is loaded, set a width equal to that of the
+                // original’s intrinsic width divided by the screen resolution.
+                newImg.onload = function() {
+                  // Clone the original image into memory so the width is
+                  // unaffected by page styles.
+                  var w = this.cloneNode(true).width;
+                  if (w > 0) {
+                    this.width = (w / resMatch);
+                  }
+                };
+                // Copy width and height from the source tag to the img element.
+                _copyAttributes(match, newImg);
+                picImg.parentNode.replaceChild(newImg, picImg);
+              }
+              // We’ve matched, so bail out of the loop here.
+              break;
+            }
+          }
+        } else {
+          // No srcset used, so just use the 'src' value.
+          picImg.src = match.getAttribute('src');
+          // Copy width and height from the source tag to the img element.
+          _copyAttributes(match, picImg);
+        }
+      }
+    }
+  };
+
+  // Run on resize and domready (w.load as a fallback)
+  if (w.addEventListener) {
+    w.addEventListener('resize', w.picturefill, false);
+    w.addEventListener('DOMContentLoaded', function() {
+      w.picturefill();
+      // Run once only.
+      w.removeEventListener('load', w.picturefill, false);
+    }, false);
+    w.addEventListener('load', w.picturefill, false);
+  }
+  else if (w.attachEvent) {
+    w.attachEvent('onload', w.picturefill);
+  }
+})(this);
diff --git a/core/modules/system/lib/Drupal/system/Tests/Common/JavaScriptTest.php b/core/modules/system/lib/Drupal/system/Tests/Common/JavaScriptTest.php
index 4c4198c..f52907f 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Common/JavaScriptTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Common/JavaScriptTest.php
@@ -97,39 +97,42 @@ function testAddExternal() {
   }
 
   /**
-   * Tests adding external JavaScript Files with the async attribute.
+   * Tests adding JavaScript files with additional attributes.
    */
-  function testAsyncAttribute() {
+  function testAttributes() {
     $default_query_string = variable_get('css_js_query_string', '0');
 
     drupal_add_library('system', 'drupal');
-    drupal_add_js('http://example.com/script.js', array('async' => TRUE));
-    drupal_add_js('core/misc/collapse.js', array('async' => TRUE));
+    drupal_add_js('http://example.com/script.js', array('attributes' => array('defer' => 'defer')));
+    drupal_add_js('core/misc/collapse.js', array('attributes' => array('defer' => 'defer')));
     $javascript = drupal_get_js();
 
-    $expected_1 = '<script src="http://example.com/script.js?' . $default_query_string . '" async="async"></script>';
-    $expected_2 = '<script src="' . file_create_url('core/misc/collapse.js') . '?' . $default_query_string . '" async="async"></script>';
+    $expected_1 = '<script src="http://example.com/script.js?' . $default_query_string . '" defer="defer"></script>';
+    $expected_2 = '<script src="' . file_create_url('core/misc/collapse.js') . '?' . $default_query_string . '" defer="defer"></script>';
 
-    $this->assertTrue(strpos($javascript, $expected_1) > 0, 'Rendered external JavaScript with correct async attribute.');
-    $this->assertTrue(strpos($javascript, $expected_2) > 0, 'Rendered internal JavaScript with correct async attribute.');
+    $this->assertTrue(strpos($javascript, $expected_1) > 0, 'Rendered external JavaScript with correct defer attribute.');
+    $this->assertTrue(strpos($javascript, $expected_2) > 0, 'Rendered internal JavaScript with correct defer attribute.');
   }
 
   /**
-   * Tests adding external JavaScript Files with the defer attribute.
+   * Tests that attributes are maintained when JS aggregation is enabled.
    */
-  function testDeferAttribute() {
+  function testAggregatedAttributes() {
+    // Enable aggregation.
+    config('system.performance')->set('preprocess.js', 1)->save();
+
     $default_query_string = variable_get('css_js_query_string', '0');
 
     drupal_add_library('system', 'drupal');
-    drupal_add_js('http://example.com/script.js', array('defer' => TRUE));
-    drupal_add_js('core/misc/collapse.js', array('defer' => TRUE));
+    drupal_add_js('http://example.com/script.js', array('attributes' => array('defer' => 'defer')));
+    drupal_add_js('core/misc/collapse.js', array('attributes' => array('defer' => 'defer')));
     $javascript = drupal_get_js();
 
     $expected_1 = '<script src="http://example.com/script.js?' . $default_query_string . '" defer="defer"></script>';
     $expected_2 = '<script src="' . file_create_url('core/misc/collapse.js') . '?' . $default_query_string . '" defer="defer"></script>';
 
-    $this->assertTrue(strpos($javascript, $expected_1) > 0, 'Rendered external JavaScript with correct defer attribute.');
-    $this->assertTrue(strpos($javascript, $expected_2) > 0, 'Rendered internal JavaScript with correct defer attribute.');
+    $this->assertTrue(strpos($javascript, $expected_1) > 0, 'Rendered external JavaScript with correct defer attribute with aggregation enabled.');
+    $this->assertTrue(strpos($javascript, $expected_2) > 0, 'Rendered internal JavaScript with correct defer attribute with aggregation enabled.');
   }
 
   /**
diff --git a/core/modules/system/lib/Drupal/system/Tests/Routing/FirstEntryFinalMatcherTest.php b/core/modules/system/lib/Drupal/system/Tests/Routing/FirstEntryFinalMatcherTest.php
index a288b9e..c44a492 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Routing/FirstEntryFinalMatcherTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Routing/FirstEntryFinalMatcherTest.php
@@ -61,7 +61,7 @@ public function testFinalMatcherStatic() {
     $matcher->setCollection($collection);
     $attributes = $matcher->matchRequest($request);
 
-    $this->assertEqual($attributes['_route'], 'route_a', 'The correct matching route was found.');
+    $this->assertEqual($attributes['_route']->getOption('_name'), 'route_a', 'The correct matching route was found.');
     $this->assertEqual($attributes['_controller'], 'foo', 'The correct controller was found.');
   }
 
@@ -82,7 +82,7 @@ public function testFinalMatcherPattern() {
     $matcher->setCollection($collection);
     $attributes = $matcher->matchRequest($request);
 
-    $this->assertEqual($attributes['_route'], 'route_a', 'The correct matching route was found.');
+    $this->assertEqual($attributes['_route']->getOption('_name'), 'route_a', 'The correct matching route was found.');
     $this->assertEqual($attributes['_controller'], 'foo', 'The correct controller was found.');
     $this->assertEqual($attributes['value'], 'narf', 'Required placeholder value found.');
   }
@@ -105,7 +105,7 @@ public function testFinalMatcherPatternDefalts() {
     $matcher->setCollection($collection);
     $attributes = $matcher->matchRequest($request);
 
-    $this->assertEqual($attributes['_route'], 'route_a', 'The correct matching route was found.');
+    $this->assertEqual($attributes['_route']->getOption('_name'), 'route_a', 'The correct matching route was found.');
     $this->assertEqual($attributes['_controller'], 'foo', 'The correct controller was found.');
     $this->assertEqual($attributes['value'], 'poink', 'Optional placeholder value used default.');
   }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Routing/HttpMethodMatcherTest.php b/core/modules/system/lib/Drupal/system/Tests/Routing/HttpMethodMatcherTest.php
index c98da2e..8055743 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Routing/HttpMethodMatcherTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Routing/HttpMethodMatcherTest.php
@@ -44,7 +44,7 @@ function __construct($test_id = NULL) {
 
     $this->fixtures = new RoutingFixtures();
   }
-  
+
   /**
    * Confirms that the HttpMethod matcher matches properly.
    */
@@ -78,7 +78,7 @@ public function testNestedMatcher() {
 
     $attributes = $matcher->matchRequest($request);
 
-    $this->assertEqual($attributes['_route'], 'route_a', 'The correct matching route was found.');
+    $this->assertEqual($attributes['_route']->getOption('_name'), 'route_a', 'The correct matching route was found.');
   }
 
   /**
diff --git a/core/modules/system/lib/Drupal/system/Tests/Routing/NestedMatcherTest.php b/core/modules/system/lib/Drupal/system/Tests/Routing/NestedMatcherTest.php
index 444785c..de29538 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Routing/NestedMatcherTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Routing/NestedMatcherTest.php
@@ -60,6 +60,6 @@ public function testNestedMatcher() {
 
     $attributes = $matcher->matchRequest($request);
 
-    $this->assertEqual($attributes['_route'], 'route_a', 'The correct matching route was found.');
+    $this->assertEqual($attributes['_route']->getOption('_name'), 'route_a', 'The correct matching route was found.');
   }
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Routing/RouterPermissionTest.php b/core/modules/system/lib/Drupal/system/Tests/Routing/RouterPermissionTest.php
new file mode 100644
index 0000000..3050e4f
--- /dev/null
+++ b/core/modules/system/lib/Drupal/system/Tests/Routing/RouterPermissionTest.php
@@ -0,0 +1,56 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\system\Tests\Routing\RouterTest.
+ */
+
+namespace Drupal\system\Tests\Routing;
+
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Description of RouterPermissionTest
+ *
+ */
+/**
+ * Functional class for the full integrated routing system.
+ */
+class RouterPermissionTest extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('block', 'router_test');
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Router Permission tests',
+      'description' => 'Function Tests for the routing permission system.',
+      'group' => 'Routing',
+    );
+  }
+
+  /**
+   * Confirms that the router can get to a controller.
+   */
+  public function testPermissionAccessDenied() {
+
+    $this->drupalGet('router_test/test5');
+    $this->assertResponse(403, 'Access denied for a route where we don\'t have a permission');
+  }
+
+  /**
+   * Confirms that our default controller logic works properly.
+   */
+  public function testPermissionAccessPassed() {
+
+    $user = $this->drupalCreateUser(array('access test5'));
+
+    $this->drupalGet('router_test/test5');
+    $this->assertRaw('test5', 'The correct string was returned because the route was successful.');
+
+  }
+}
diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTest.php
index bd6c93b..f1308c5 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTest.php
@@ -187,4 +187,19 @@ function testRegistryRebuild() {
   function testClassLoading() {
     new ThemeClass();
   }
+
+  /**
+   * Tests drupal_find_theme_templates().
+   */
+  public function testFindThemeTemplates() {
+    $cache = array();
+
+    // Prime the theme cache.
+    foreach (module_implements('theme') as $module) {
+      _theme_process_registry($cache, $module, 'module', $module, drupal_get_path('module', $module));
+    }
+
+    $templates = drupal_find_theme_templates($cache, '.tpl.php', drupal_get_path('theme', 'test_theme'));
+    $this->assertEqual($templates['node__1']['template'], 'node--1', 'Template node--1.tpl.php was found in test_theme.');
+  }
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTestTwig.php b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTestTwig.php
new file mode 100644
index 0000000..6a9d988
--- /dev/null
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTestTwig.php
@@ -0,0 +1,70 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\system\Tests\Theme\ThemeTest.
+ */
+
+namespace Drupal\system\Tests\Theme;
+
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Tests low-level theme functions.
+ */
+class ThemeTestTwig extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('theme_test');
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Twig Engine',
+      'description' => 'Test theme functions with twig.',
+      'group' => 'Theme',
+    );
+  }
+
+  function setUp() {
+    parent::setUp();
+    theme_enable(array('test_theme_twig'));
+  }
+
+  /**
+   * Ensures a themes template is overrideable based on the 'template' filename.
+   */
+  function testTemplateOverride() {
+    variable_set('theme_default', 'test_theme_twig');
+    $this->drupalGet('theme-test/template-test');
+    $this->assertText('Success: Template overridden.', t('Template overridden by defined \'template\' filename.'));
+  }
+
+  /**
+   * Tests drupal_find_theme_templates
+   */
+  function testFindThemeTemplates() {
+
+    $cache = array();
+
+    // Prime the theme cache
+    foreach (module_implements('theme') as $module) {
+      _theme_process_registry($cache, $module, 'module', $module, drupal_get_path('module', $module));
+    }
+
+    // Check for correct content
+    // @todo Remove this tests once double engine code is removed
+
+    $this->assertEqual($cache['node']['template_file'], 'core/modules/node/templates/node.twig', 'Node is using node.twig as template file');
+    $this->assertEqual($cache['node']['engine'], 'twig', 'Node is using twig engine');
+
+    $this->assertEqual($cache['theme_test_template_test']['template_file'], 'core/modules/system/tests/modules/theme_test/templates/theme_test.template_test.tpl.php', 'theme_test is using theme_test.template_test.tpl.php as template file');
+    $this->assertEqual($cache['theme_test_template_test']['engine'], 'phptemplate', 'theme_test is using phptemplate as engine.');
+
+    $templates = drupal_find_theme_templates($cache, '.twig', drupal_get_path('theme', 'test_theme_twig'));
+    $this->assertEqual($templates['node__1']['template'], 'node--1', 'Template node--1.twig was found in test_theme_twig.');
+  }
+}
diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/TwigReferenceObjectTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/TwigReferenceObjectTest.php
new file mode 100644
index 0000000..88a4d22
--- /dev/null
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/TwigReferenceObjectTest.php
@@ -0,0 +1,18 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\system\Tests\Theme\TwigReferenceObjectTest.
+ */
+
+namespace Drupal\system\Tests\Theme;
+
+/**
+ * TwigReferenceObjectTest class.
+ */
+class TwigReferenceObjectTest {
+  public function __construct($nid, $title) {
+    $this->nid = $nid;
+    $this->title = $title;
+  }
+}
diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/TwigReferenceUnitTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/TwigReferenceUnitTest.php
new file mode 100644
index 0000000..0f9534e
--- /dev/null
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/TwigReferenceUnitTest.php
@@ -0,0 +1,147 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\system\Tests\Theme\TwigReferenceUnitTest.
+ */
+
+namespace Drupal\system\Tests\Theme;
+
+use Drupal\simpletest\UnitTestBase;
+use Drupal\Core\Template\TwigReference;
+use Drupal\Core\Template\TwigReferenceFunctions;
+
+/**
+ * Unit tests for TwigReference class.
+ */
+class TwigReferenceUnitTest extends UnitTestBase {
+  public static function getInfo() {
+    return array(
+      'name' => 'Theme Twig References',
+      'description' => 'Tests TwigReference functions',
+      'group' => 'Theme',
+    );
+  }
+
+  function setUp() {
+    parent::setUp();
+    $this->variables = array(
+      'foo' => 'bar',
+      'baz' => array(
+        'foo' => '42',
+        'bar' => '23',
+      ),
+      'node' => new TwigReferenceObjectTest(
+        42,
+        'test node'
+      )
+    );
+  }
+
+  /**
+   * Test function for TwigReference class
+   */
+  function testTwigReference() {
+    // Create a new TwigReference wrapper
+    $wrapper = new TwigReference();
+    $wrapper->setReference($this->variables);
+
+    // Check that strings are returned as strings
+    $foo = $wrapper['foo'];
+    $this->assertEqual($foo, $this->variables['foo'], 'String returned from TwigReference is the same');
+    $this->assertTrue(is_string($foo), 'String returned from TwigReference is of type string');
+
+    // Check that arrays are wrapped again as TwigReference objects
+    $baz = $wrapper['baz'];
+    $this->assertTrue(is_object($baz), 'Array returned from TwigReference is of type object');
+    $this->assertTrue($baz instanceof TwigReference, 'Array returned from TwigReference is instance of TwigReference');
+
+    // Check that getReference is giving back a reference to the original array
+
+    $ref = &$baz->getReference();
+    $this->assertTrue(is_array($ref), 'getReference returns an array');
+
+    // Now modify $ref
+    $ref['#hidden'] = TRUE;
+    $this->assertEqual($ref['#hidden'], $this->variables['baz']['#hidden'], 'Property set on reference is passed to original array.');
+    $this->assertEqual($ref['#hidden'], $baz['#hidden'], 'Property set on reference is passed to wrapper.');
+
+    // Now modify $baz
+    $baz['hi'] = 'hello';
+
+    $this->assertEqual($baz['hi'], $this->variables['baz']['hi'], 'Property set on TwigReference object is passed to original array.');
+    $this->assertEqual($baz['hi'], $ref['hi'], 'Property set on TwigReference object is passed to reference.');
+
+    // Check that an object is passed through directly
+    $node = $wrapper['node'];
+    $this->assertTrue(is_object($node), 'Object returned from TwigReference is of type object');
+    $this->assertTrue($node instanceof TwigReferenceObjectTest, 'Object returned from TwigReference is instance of TwigReferenceObjectTest');
+  }
+
+  /**
+   * Test function for TwigReferenceFunctions class
+   */
+  function testTwigReferenceFunctions() {
+
+    // Create wrapper
+    $content = &$this->variables;
+
+    // Use twig nomenclature
+    $context['content'] = $content;
+
+    // Twig converts {{ hide(content.baz) }} to the following code
+
+    // This will have failed, because getAttribute returns a value and not a reference
+
+    try {
+      if (isset($context["content"])) {
+        $_content_ = $context["content"];
+      }
+      else {
+        $_content_ = NULL;
+      }
+      TwigReferenceFunctions::hide($this->getAttribute($_content_, "baz"));
+    }
+    catch (Exception $e) {
+      // Catch the critical warning that a value was passed by reference
+    }
+    $this->assertFalse(isset($content['baz']['#printed']), 'baz is not hidden in content after hide() via value');
+
+    // Now lets do the same with some TwigReference magic!
+
+    $content_wrapper = new TwigReference();
+    $content_wrapper->setReference($content);
+    $context['content'] = $content_wrapper;
+
+    // Twig converts {{ hide(content.baz) }} to the following code
+
+    // This will succeed, because getAttribute returns a value, but it is an object
+
+    if (isset($context["content"])) {
+      $_content_ = $context["content"];
+    }
+    else {
+      $_content_ = NULL;
+    }
+    TwigReferenceFunctions::hide($this->getAttribute($_content_, "baz"));
+
+    $this->assertTrue(isset($content['baz']['#printed']), 'baz is hidden in content after hide() via TwigReference object');
+
+    $type = TwigReferenceFunctions::gettype($this->getAttribute($_content_, "baz"));
+    $this->assertEqual($type, 'array', 'Type returned via TwigReferenceFunctions:: is an array.');
+
+    $type = gettype($this->getAttribute($_content_, "baz"));
+    $this->assertEqual($type, 'object', 'Type returned without TwigReferenceFunctions:: is an object.');
+  }
+
+  /**
+   *  Helper function to somehow simulate Twigs getAttribute function
+   */
+  public function getAttribute($array, $offset) {
+    if (isset($array[$offset])) {
+      return $array[$offset];
+    }
+
+    return NULL;
+  }
+}
diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index 2d09534..0965579 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -566,51 +566,6 @@ function hook_menu_get_item_alter(&$router_item, $path, $original_map) {
 }
 
 /**
- * Defines routes in the new router system.
- *
- * A route is a Symfony Route object.  See the Symfony documentation for more
- * details on the available options.  Of specific note:
- *  - _controller: This is the PHP callable that will handle a request matching
- *              the route.
- *  - _content: This is the PHP callable that will handle the body of a request
- *              matching this route.  A default controller will provide the page
- *              rendering around it.
- *
- * Typically you will only specify one or the other of those properties.
- *
- * @deprecated
- *   This mechanism for registering routes is temporary. It will be replaced
- *   by a more robust mechanism in the near future.  It is documented here
- *   only for completeness.
- */
-function hook_route_info() {
-  $collection = new RouteCollection();
-
-  $route = new Route('router_test/test1', array(
-    '_controller' => '\Drupal\router_test\TestControllers::test1'
-  ));
-  $collection->add('router_test_1', $route);
-
-  $route = new Route('router_test/test2', array(
-    '_content' => '\Drupal\router_test\TestControllers::test2'
-  ));
-  $collection->add('router_test_2', $route);
-
-  $route = new Route('router_test/test3/{value}', array(
-    '_content' => '\Drupal\router_test\TestControllers::test3'
-  ));
-  $collection->add('router_test_3', $route);
-
-  $route = new Route('router_test/test4/{value}', array(
-    '_content' => '\Drupal\router_test\TestControllers::test4',
-    'value' => 'narf',
-  ));
-  $collection->add('router_test_4', $route);
-
-  return $collection;
-}
-
-/**
  * Define menu items and page callbacks.
  *
  * This hook enables modules to register paths in order to define how URL
diff --git a/core/modules/system/system.theme-rtl.css b/core/modules/system/system.theme-rtl.css
index b13345a..eaf351b 100644
--- a/core/modules/system/system.theme-rtl.css
+++ b/core/modules/system/system.theme-rtl.css
@@ -67,18 +67,9 @@ ul.menu {
 /**
  * Markup generated by theme_menu_local_tasks().
  */
-ul.primary {
-  padding: 0 1em 0 0;
-}
-ul.primary li a {
-  margin-right: 5px;
-  margin-left: 0.5em;
-}
-ul.secondary li {
-  border-left: 1px solid #ccc;
-  border-right: none;
-  display: inline;
-  padding: 0 1em;
+.tabs > li {
+  margin-left: 0.3em;
+  margin-right: 0;
 }
 
 /**
diff --git a/core/modules/system/system.theme.css b/core/modules/system/system.theme.css
index 84c0078..61303d2 100644
--- a/core/modules/system/system.theme.css
+++ b/core/modules/system/system.theme.css
@@ -306,55 +306,29 @@ ul.inline li {
 /**
  * Markup generated by theme_menu_local_tasks().
  */
-ul.primary {
-  border-bottom: 1px solid #bbb;
-  border-collapse: collapse;
-  height: auto;
-  line-height: normal;
+div.tabs {
+  margin: 1em 0;
+}
+ul.tabs {
   list-style: none;
-  margin: 5px;
-  padding: 0 0 0 1em; /* LTR */
-  white-space: nowrap;
+  margin: 0 0 0.5em;
+  padding: 0;
 }
-ul.primary li {
-  display: inline;
+.tabs > li {
+  display: inline-block;
+  margin-right: 0.3em; /* LTR */
 }
-ul.primary li a {
-  background-color: #ddd;
-  border-color: #bbb;
-  border-style: solid solid none solid;
-  border-width: 1px;
-  height: auto;
-  margin-right: 0.5em; /* LTR */
-  padding: 0 1em;
+.tabs a {
+  display: block;
+  padding: 0.2em 1em;
   text-decoration: none;
 }
-ul.primary li.active a {
-  background-color: #fff;
-  border: 1px solid #bbb;
-  border-bottom: 1px solid #fff;
-}
-ul.primary li a:hover {
+.tabs a.active {
   background-color: #eee;
-  border-color: #ccc;
-  border-bottom-color: #eee;
-}
-ul.secondary {
-  border-bottom: 1px solid #bbb;
-  padding: 0.5em 1em;
-  margin: 5px;
-}
-ul.secondary li {
-  border-right: 1px solid #ccc; /* LTR */
-  display: inline;
-  padding: 0 1em;
-}
-ul.secondary a {
-  padding: 0;
-  text-decoration: none;
 }
-ul.secondary a.active {
-  border-bottom: 4px solid #999;
+.tabs a:focus,
+.tabs a:hover {
+  background-color: #f5f5f5;
 }
 
 /**
diff --git a/core/modules/system/templates/datetime.twig b/core/modules/system/templates/datetime.twig
new file mode 100644
index 0000000..5ea386e
--- /dev/null
+++ b/core/modules/system/templates/datetime.twig
@@ -0,0 +1,28 @@
+{#
+/**
+ * Returns HTML for a date / time.
+ *
+ * Available variables
+ * - timestamp: (optional) A UNIX timestamp for the datetime attribute. If the
+ *   datetime cannot be represented as a UNIX timestamp, use a valid datetime
+ *   attribute value in attributes.datetime.
+ * - text: (optional) The content to display within the <time> element. Set
+ *   'html' to TRUE if this value is already sanitized for output in HTML.
+ *   Defaults to a human-readable representation of the timestamp value or the
+ *   datetime attribute value using format_date().
+ * - attributes: (optional) HTML attributes to apply to the <time> element.
+ *   A datetime attribute in 'attributes' overrides the 'timestamp'. To
+ *   create a valid datetime attribute value from a UNIX timestamp, use
+ *   format_date() with one of the predefined 'html_*' formats.
+ * - html: (optional) Whether 'text' is HTML markup (TRUE) or plain-text
+ *   (FALSE). Defaults to FALSE. For example, to use a SPAN tag within the
+ *   TIME element, this must be set to TRUE, or the SPAN tag will be escaped.
+ *   It is the responsibility of the caller to properly sanitize the value
+ *   contained in 'text' (or within the SPAN tag in aforementioned example).
+ *
+ * @see template_preprocess_datetime()
+ * @see http://www.w3.org/TR/html5-author/the-time-element.html#attr-time-datetime
+ */
+#}
+{# @todo Revisit once http://drupal.org/node/1825952 is resolved. #}
+<time class="{{ attributes.class }}" {{ attributes }}>{{ html ? text|raw : text|escape }}</time>
diff --git a/core/modules/system/tests/modules/router_test/lib/Drupal/router_test/TestControllers.php b/core/modules/system/tests/modules/router_test/lib/Drupal/router_test/TestControllers.php
index fa92fd8..ca6605a 100644
--- a/core/modules/system/tests/modules/router_test/lib/Drupal/router_test/TestControllers.php
+++ b/core/modules/system/tests/modules/router_test/lib/Drupal/router_test/TestControllers.php
@@ -30,4 +30,8 @@ public function test4($value) {
     return $value;
   }
 
+  public function test5() {
+    return new Response('test5');
+  }
+
 }
diff --git a/core/modules/system/tests/modules/router_test/router_test.module b/core/modules/system/tests/modules/router_test/router_test.module
index 4da939d..bbaedd0 100644
--- a/core/modules/system/tests/modules/router_test/router_test.module
+++ b/core/modules/system/tests/modules/router_test/router_test.module
@@ -1,34 +1,13 @@
 <?php
 
-use Symfony\Component\Routing\Route;
-use Symfony\Component\Routing\RouteCollection;
-
 /**
- * Implements hook_router_info().
+ * Implements hook_permission().
  */
-function router_test_route_info() {
-  $collection = new RouteCollection();
-
-  $route = new Route('router_test/test1', array(
-    '_controller' => '\Drupal\router_test\TestControllers::test1'
-  ));
-  $collection->add('router_test_1', $route);
-
-  $route = new Route('router_test/test2', array(
-    '_content' => '\Drupal\router_test\TestControllers::test2'
-  ));
-  $collection->add('router_test_2', $route);
-
-  $route = new Route('router_test/test3/{value}', array(
-    '_content' => '\Drupal\router_test\TestControllers::test3'
-  ));
-  $collection->add('router_test_3', $route);
-
-  $route = new Route('router_test/test4/{value}', array(
-    '_content' => '\Drupal\router_test\TestControllers::test4',
-    'value' => 'narf',
-  ));
-  $collection->add('router_test_4', $route);
-
-  return $collection;
+function router_test_permission() {
+  return array(
+    'access test5' =>  array(
+      'title' => t('Access test5 route'),
+      'description' => t('Test permission only.'),
+    ),
+  );
 }
diff --git a/core/modules/system/tests/modules/router_test/router_test.routing.yml b/core/modules/system/tests/modules/router_test/router_test.routing.yml
new file mode 100644
index 0000000..a49dd80
--- /dev/null
+++ b/core/modules/system/tests/modules/router_test/router_test.routing.yml
@@ -0,0 +1,20 @@
+router_test_1:
+  pattern: '/router_test/test1'
+  defaults:
+    _controller: '\Drupal\router_test\TestControllers::test1'
+
+router_test_2:
+  pattern: '/router_test/test2'
+  defaults:
+    _content: '\Drupal\router_test\TestControllers::test2'
+
+router_test_3:
+  pattern: '/router_test/test3/{value}'
+  defaults:
+    _content: '\Drupal\router_test\TestControllers::test3'
+
+router_test_4:
+  pattern: '/router_test/test4/{value}'
+  defaults:
+    _content: '\Drupal\router_test\TestControllers::test4'
+    value: 'narf'
diff --git a/core/modules/system/tests/modules/theme_test/templates/theme_test.template_test.tpl.php b/core/modules/system/tests/modules/theme_test/templates/theme_test.template_test.tpl.php
new file mode 100644
index 0000000..cde8faa
--- /dev/null
+++ b/core/modules/system/tests/modules/theme_test/templates/theme_test.template_test.tpl.php
@@ -0,0 +1,2 @@
+<!-- Output for Theme API test -->
+Fail: Template not overridden.
diff --git a/core/modules/system/tests/modules/theme_test/theme_test.module b/core/modules/system/tests/modules/theme_test/theme_test.module
index a05bc46..f231b49 100644
--- a/core/modules/system/tests/modules/theme_test/theme_test.module
+++ b/core/modules/system/tests/modules/theme_test/theme_test.module
@@ -27,6 +27,7 @@ function theme_test_system_theme_info() {
   $themes['test_theme'] = drupal_get_path('module', 'system') . '/tests/themes/test_theme/test_theme.info';
   $themes['test_basetheme'] = drupal_get_path('module', 'system') . '/tests/themes/test_basetheme/test_basetheme.info';
   $themes['test_subtheme'] = drupal_get_path('module', 'system') . '/tests/themes/test_subtheme/test_subtheme.info';
+  $themes['test_theme_twig'] = drupal_get_path('module', 'system') . '/tests/themes/test_theme_twig/test_theme_twig.info';
   return $themes;
 }
 
diff --git a/core/modules/system/tests/modules/theme_test/theme_test.template_test.tpl.php b/core/modules/system/tests/modules/theme_test/theme_test.template_test.tpl.php
deleted file mode 100644
index cde8faa..0000000
--- a/core/modules/system/tests/modules/theme_test/theme_test.template_test.tpl.php
+++ /dev/null
@@ -1,2 +0,0 @@
-<!-- Output for Theme API test -->
-Fail: Template not overridden.
diff --git a/core/modules/system/tests/themes/test_theme/node--1.tpl.php b/core/modules/system/tests/themes/test_theme/node--1.tpl.php
new file mode 100644
index 0000000..81974ce
--- /dev/null
+++ b/core/modules/system/tests/themes/test_theme/node--1.tpl.php
@@ -0,0 +1,4 @@
+<?php
+  // node--1.tpl.php - Dummy file for finding the template
+?>
+Node Content Dummy
diff --git a/core/modules/system/tests/themes/test_theme_twig/node--1.twig b/core/modules/system/tests/themes/test_theme_twig/node--1.twig
new file mode 100644
index 0000000..79148f1
--- /dev/null
+++ b/core/modules/system/tests/themes/test_theme_twig/node--1.twig
@@ -0,0 +1,4 @@
+{#
+  // node--1.twig - Dummy file for finding the template
+#}
+Node Content Dummy
diff --git a/core/modules/system/tests/themes/test_theme_twig/template.php b/core/modules/system/tests/themes/test_theme_twig/template.php
new file mode 100644
index 0000000..a4abe2d
--- /dev/null
+++ b/core/modules/system/tests/themes/test_theme_twig/template.php
@@ -0,0 +1,2 @@
+<?php
+
diff --git a/core/modules/system/tests/themes/test_theme_twig/test_theme_twig.info b/core/modules/system/tests/themes/test_theme_twig/test_theme_twig.info
new file mode 100644
index 0000000..5097adb
--- /dev/null
+++ b/core/modules/system/tests/themes/test_theme_twig/test_theme_twig.info
@@ -0,0 +1,5 @@
+name = Test theme for Twig
+description = Theme for testing the theme system with twig engine
+engine = twig
+core = 8.x
+hidden = TRUE
diff --git a/core/modules/system/tests/themes/test_theme_twig/theme_test.template_test.twig b/core/modules/system/tests/themes/test_theme_twig/theme_test.template_test.twig
new file mode 100644
index 0000000..6cda319
--- /dev/null
+++ b/core/modules/system/tests/themes/test_theme_twig/theme_test.template_test.twig
@@ -0,0 +1,2 @@
+{# Output for Theme API test #}
+Success: Template overridden.
diff --git a/core/themes/bartik/css/style-rtl.css b/core/themes/bartik/css/style-rtl.css
index 703a8f8..d9eb3dc 100644
--- a/core/themes/bartik/css/style-rtl.css
+++ b/core/themes/bartik/css/style-rtl.css
@@ -194,6 +194,8 @@ a.button {
   zoom: 1;
 }
 .tabs ul.secondary li {
+  border-left: 1px solid #ccc;
+  border-right: none;
   float: right;
 }
 .tabs ul.secondary li:first-child {
diff --git a/core/themes/bartik/css/style.css b/core/themes/bartik/css/style.css
index 29152bb..20f9136 100644
--- a/core/themes/bartik/css/style.css
+++ b/core/themes/bartik/css/style.css
@@ -960,16 +960,20 @@ ul.links {
 
 /* --------------- System Tabs  --------------- */
 
-.tabs {
+div.tabs {
   font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
   margin-bottom: 20px;
 }
 .tabs ul.primary {
+  border-collapse: collapse;
+  height: auto;
+  line-height: normal;
   padding: 0 3px;
   margin: 0;
   overflow: hidden;
   border: none;
   background: transparent url(../images/tabs-border.png) repeat-x left bottom;
+  white-space: nowrap;
 }
 .tabs ul.primary li {
   display: block;
@@ -983,6 +987,9 @@ ul.links {
 .tabs ul.primary li a {
   color: #000;
   background-color: #ededed;
+  border-color: #bbb;
+  border-style: solid solid none solid;
+  border-width: 1px;
   height: 1.8em;
   line-height: 1.9;
   display: block;
@@ -996,14 +1003,20 @@ ul.links {
 }
 .tabs ul.primary li.active a {
   background-color: #ffffff;
+  border: 1px solid #bbb;
+  border-bottom: 1px solid #fff;
 }
 .tabs ul.secondary {
   border-bottom: none;
+  margin: 5px;
   padding: 0.5em 0;
 }
 .tabs ul.secondary li {
+  border-right: 1px solid #ccc; /* LTR */
   display: block;
   float: left; /* LTR */
+  margin: 0;
+  padding: 0 1em;
 }
 .tabs ul.secondary li:last-child {
   border-right: none; /* LTR */
@@ -1012,7 +1025,9 @@ ul.links {
   padding-left: 0; /* LTR */
 }
 .tabs ul.secondary li a {
+  display: inline;
   padding: 0.25em 0.5em;
+  text-decoration: none;
 }
 .tabs ul.secondary li a.active {
   background: #f2f2f2;
diff --git a/core/themes/engines/twig/twig.engine b/core/themes/engines/twig/twig.engine
new file mode 100644
index 0000000..e7de4cf
--- /dev/null
+++ b/core/themes/engines/twig/twig.engine
@@ -0,0 +1,126 @@
+<?php
+
+/**
+ * @file
+ * Handles integration of Twig templates with the Drupal theme system.
+ */
+use Drupal\Core\Template\TwigReference;
+
+/**
+ * Implements hook_theme().
+ */
+function twig_theme($existing, $type, $theme, $path) {
+  return drupal_find_theme_templates($existing, '.twig', $path);
+}
+
+/**
+ * Implements hook_extension().
+ */
+function twig_extension() {
+  return '.twig';
+}
+
+/**
+ * Implements hook_init().
+ */
+function twig_init($template) {
+  $file = dirname($template->filename) . '/template.php';
+  if (file_exists($file)) {
+    include_once DRUPAL_ROOT . '/' . $file;
+  }
+}
+
+/**
+ * Render twig templates.
+ *
+ * This retrieves the Twig_Environment from the Drupal Injection container and
+ * renders the template.
+ *
+ * @param $template_file
+ *   The filename of the template to render.
+ * @param $variables
+ *   A keyed array of variables that will appear in the output.
+ *
+ * @return
+ *   The output generated by the template.
+ */
+function twig_render_template($template_file, $variables) {
+  $variables['_references']=array();
+  return drupal_container()->get('twig')->loadTemplate($template_file)->render($variables);
+}
+
+/**
+ * Wrapper around render() for twig printed output.
+ *
+ * If an object is passed that has no __toString method an exception is thrown;
+ * other objects are casted to string. However in the case that the object is an
+ * instance of a Twig_Markup object it is returned directly to support auto
+ * escaping.
+ *
+ * If an array is passed it is rendered via render() and scalar values are
+ * returned directly.
+ *
+ * @param mixed $arg
+ *   String, Object or Render Array
+ *
+ * @return
+ *   The rendered output or an Twig_Markup object.
+ *
+ * @see render
+ * @see TwigNodeVisitor
+ */
+function twig_render($arg) {
+  if ($arg instanceof TwigReference) {
+    $arg = &$arg->getReference();
+  }
+
+  // == is true also for empty arrays
+  if ($arg == NULL) {
+    return NULL;
+  }
+
+  // Keep Twig_Markup objects intact to prepare for later autoescaping support
+  if ($arg instanceOf Twig_Markup) {
+    return $arg;
+  }
+
+  if (is_scalar($arg)) {
+    return $arg;
+  }
+
+  if (is_object($arg)) {
+    if (method_exists($arg, '__toString')) {
+      return (string) $arg;
+    }
+    throw new Exception(t('Object of type "@class" cannot be printed.', array('@class' => get_class($arg))));
+  }
+
+  // This is a normal render array.
+  return render($arg);
+}
+
+/**
+ * Wrapper around hide() that does not return the content.
+ *
+ * @see hide
+ */
+function twig_hide($element) {
+  if ($element instanceof TwigReference) {
+    $element = &$element->getReference();
+    hide($element);
+  }
+  // @todo Add warning in else case
+}
+
+/**
+ * Wrapper around show() that does not return the content.
+ *
+ * @see show
+ */
+function twig_show($element) {
+  if ($element instanceof TwigReference) {
+    $element = &$element->getReference();
+    show($element);
+  }
+  // @todo Add warning in else case
+}
diff --git a/core/themes/seven/style.css b/core/themes/seven/style.css
index a517d64..65abcc7 100644
--- a/core/themes/seven/style.css
+++ b/core/themes/seven/style.css
@@ -974,9 +974,6 @@ ol.task-list li.done {
   line-height: 1.54em;
   margin: 0;
 }
-#overlay-tabs li {
-  margin: 0 -2px;
-}
 .overlay ul.secondary {
   background: transparent none;
   margin: -1.4em 0 0.3em 0; /* LTR */
diff --git a/core/update.php b/core/update.php
index 968e8f4..83c6c10 100644
--- a/core/update.php
+++ b/core/update.php
@@ -458,6 +458,7 @@ function update_check_requirements($skip_warnings = FALSE) {
 $container->register('router.dumper', '\Drupal\Core\Routing\MatcherDumper')
   ->addArgument(new Reference('database'));
 $container->register('router.builder', 'Drupal\Core\Routing\RouteBuilder')
+  ->addArgument(new Reference('dispatcher'))
   ->addArgument(new Reference('router.dumper'))
   ->addArgument(new Reference('lock'));