diff --git a/core/includes/common.inc b/core/includes/common.inc
index d551cbb..dd04e5d 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -3690,7 +3690,7 @@ function drupal_prepare_page($page, $legacy = FALSE) {
   // in the page with defaults.
   if (is_string($page) || (is_array($page) && (!isset($page['#type']) || ($page['#type'] != 'page')))) {
     drupal_set_page_content($page);
-    $page = $legacy ? element_info('page') : element_info('page_body');
+    $page = $legacy ? element_info('page') : element_info('page');
   }
 
   // Modules can add elements to $page as needed in hook_page_build().
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 37644a7..e582ea0 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2510,7 +2510,7 @@ function _template_preprocess_default_variables() {
  *
  * @see system_elements()
  */
-function template_preprocess_html_page(&$variables) {
+function template_preprocess_html(&$variables) {
 
   /** @var $page \Drupal\Core\Page\HtmlPage */
   $page = $variables['page_object'];
@@ -2644,157 +2644,6 @@ function template_preprocess_html_page(&$variables) {
 }
 
 /**
- * Prepares variables for HTML document templates.
- *
- * This is specifically for the legacy router only.
- *
- * Default template: html.html.twig.
- *
- * @param array $variables
- *   An associative array containing:
- *   - page: A render element representing the page.
- *
- * @see system_elements()
- */
-function template_preprocess_html(&$variables) {
-  $language_interface = language(Language::TYPE_INTERFACE);
-
-  // Compile a list of classes that are going to be applied to the body element.
-  // This allows advanced theming based on context (home page, node of certain type, etc.).
-  $variables['attributes']['class'][] = 'html';
-  // Add a class that tells us whether we're on the front page or not.
-  $variables['attributes']['class'][] = $variables['is_front'] ? 'front' : 'not-front';
-  // Add a class that tells us whether the page is viewed by an authenticated user or not.
-  $variables['attributes']['class'][] = $variables['logged_in'] ? 'logged-in' : 'not-logged-in';
-
-  // Add information about the number of sidebars.
-  if (!empty($variables['page']['sidebar_first']) && !empty($variables['page']['sidebar_second'])) {
-    $variables['attributes']['class'][] = 'two-sidebars';
-  }
-  elseif (!empty($variables['page']['sidebar_first'])) {
-    $variables['attributes']['class'][] = 'one-sidebar';
-    $variables['attributes']['class'][] = 'sidebar-first';
-  }
-  elseif (!empty($variables['page']['sidebar_second'])) {
-    $variables['attributes']['class'][] = 'one-sidebar';
-    $variables['attributes']['class'][] = 'sidebar-second';
-  }
-  else {
-    $variables['attributes']['class'][] = 'no-sidebars';
-  }
-
-  // Populate the body classes.
-  if ($suggestions = theme_get_suggestions(arg(), 'page', '-')) {
-    foreach ($suggestions as $suggestion) {
-      if ($suggestion != 'page-front') {
-        // Add current suggestion to page classes to make it possible to theme
-        // the page depending on the current page type (e.g. node, admin, user,
-        // etc.) as well as more specific data like node-12 or node-edit.
-        $variables['attributes']['class'][] = drupal_html_class($suggestion);
-      }
-    }
-  }
-
-  // If on an individual node page, add the node type to body classes.
-  if ($node = menu_get_object()) {
-    $variables['attributes']['class'][] = drupal_html_class('node-type-' . $node->getType());
-  }
-
-  // Initializes attributes which are specific to the html and body elements.
-  $variables['html_attributes'] = new Attribute;
-
-  // HTML element attributes.
-  $variables['html_attributes']['lang'] = $language_interface->id;
-  $variables['html_attributes']['dir'] = $language_interface->direction ? 'rtl' : 'ltr';
-
-  // Add favicon.
-  if (theme_get_setting('features.favicon')) {
-    $favicon = theme_get_setting('favicon.url');
-    $type = theme_get_setting('favicon.mimetype');
-    drupal_add_html_head_link(array('rel' => 'shortcut icon', 'href' => drupal_strip_dangerous_protocols($favicon), 'type' => $type));
-  }
-
-  $site_config = Drupal::config('system.site');
-  // Construct page title.
-  if (isset($variables['page']['#title'])) {
-    $head_title = array(
-      'title' => strip_tags($variables['page']['#title']),
-      'name' => String::checkPlain($site_config->get('name')),
-    );
-  }
-  elseif (drupal_get_title()) {
-    $head_title = array(
-      'title' => strip_tags(drupal_get_title()),
-      'name' => check_plain($site_config->get('name')),
-    );
-  }
-  else {
-    $head_title = array('name' => check_plain($site_config->get('name')));
-    if ($site_config->get('slogan')) {
-      $head_title['slogan'] = strip_tags(filter_xss_admin($site_config->get('slogan')));
-    }
-  }
-
-  $variables['head_title_array'] = $head_title;
-  $variables['head_title'] = implode(' | ', $head_title);
-
-  // Display the html.tpl.php's default mobile metatags for responsive design.
-  $elements = array(
-    'MobileOptimized' => array(
-      '#tag' => 'meta',
-      '#attributes' => array(
-        'name' => 'MobileOptimized',
-        'content' => 'width',
-      ),
-    ),
-    'HandheldFriendly' => array(
-      '#tag' => 'meta',
-      '#attributes' => array(
-        'name' => 'HandheldFriendly',
-        'content' => 'true',
-      ),
-    ),
-    'viewport' => array(
-      '#tag' => 'meta',
-      '#attributes' => array(
-        'name' => 'viewport',
-        'content' => 'width=device-width',
-      ),
-    ),
-  );
-  foreach ($elements as $name => $element) {
-    drupal_add_html_head($element, $name);
-  }
-
-  // Populate the page template suggestions.
-  if ($suggestions = theme_get_suggestions(arg(), 'html')) {
-    $variables['theme_hook_suggestions'] = $suggestions;
-  }
-
-  drupal_add_library('system', 'html5shiv', TRUE);
-
-  // Render page_top and page_bottom into top level variables.
-  $variables['page_top'] = array();
-  if (isset($variables['page']['page_top'])) {
-    $variables['page_top'] = drupal_render($variables['page']['page_top']);
-  }
-  $variables['page_bottom'] = array();
-  if (isset($variables['page']['page_bottom'])) {
-    $variables['page_bottom'][]['#markup'] = drupal_render($variables['page']['page_bottom']);
-  }
-
-  // Add footer scripts as '#markup' so they can be rendered with other
-  // elements in page_bottom.
-  $footer_scripts = new RenderWrapper('drupal_get_js', array('footer'));
-  $variables['page_bottom'][] = array('#markup' => $footer_scripts);
-
-  // Wrap function calls in an object so they can be called when printed.
-  $variables['head'] = new RenderWrapper('drupal_get_html_head');
-  $variables['styles'] = new RenderWrapper('drupal_get_css');
-  $variables['scripts'] = new RenderWrapper('drupal_get_js');
-}
-
-/**
  * Prepares variables for the page template.
  *
  * Default template: page.html.twig.
@@ -3165,10 +3014,6 @@ function drupal_common_theme() {
   return array(
     // From theme.inc.
     'html' => array(
-      'render element' => 'page',
-      'template' => 'html',
-    ),
-    'html_page' => array(
       'variables' => array('page_object' => NULL),
       'template' => 'html',
     ),
diff --git a/core/lib/Drupal/Core/Controller/ExceptionController.php b/core/lib/Drupal/Core/Controller/ExceptionController.php
index d010819..0f8f2c4 100644
--- a/core/lib/Drupal/Core/Controller/ExceptionController.php
+++ b/core/lib/Drupal/Core/Controller/ExceptionController.php
@@ -147,7 +147,7 @@ public function on403Html(FlattenException $exception, Request $request) {
       $page->setTitle(t('Access denied'));
       $page->setStatusCode(403);
 
-      $output = theme('html_page', array('page_object' => $page));
+      $output = theme('html', array('page_object' => $page));
       $response = new Response($output, $page->getStatusCode());
 
       return $response;
@@ -223,7 +223,7 @@ public function on404Html(FlattenException $exception, Request $request) {
       $page->setTitle(t('Page not found'));
       $page->setStatusCode(404);
 
-      $output = theme('html_page', array('page_object' => $page));
+      $output = theme('html', array('page_object' => $page));
       $response = new Response($output, $page->getStatusCode());
     }
 
diff --git a/core/lib/Drupal/Core/Controller/HtmlFormController.php b/core/lib/Drupal/Core/Controller/HtmlFormController.php
index 5f5ca4f..246611a 100644
--- a/core/lib/Drupal/Core/Controller/HtmlFormController.php
+++ b/core/lib/Drupal/Core/Controller/HtmlFormController.php
@@ -51,7 +51,7 @@ public function __construct(ControllerResolverInterface $resolver, ContainerInte
   protected function getFormObject(Request $request, $form_arg) {
     // If this is a class, instantiate it.
     if (class_exists($form_arg)) {
-      if (in_array('Drupal\Core\Controller\ControllerInterface', class_implements($form_arg))) {
+      if (in_array('Drupal\Core\DependencyInjection\ContainerInjectionInterface', class_implements($form_arg))) {
         return $form_arg::create($this->container);
       }
 
diff --git a/core/lib/Drupal/Core/EventSubscriber/ViewSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/ViewSubscriber.php
index 6d59657..35a57d3 100644
--- a/core/lib/Drupal/Core/EventSubscriber/ViewSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/ViewSubscriber.php
@@ -41,7 +41,7 @@ public function __construct(ContentNegotiation $negotiation) {
   public function onHtmlPage(GetResponseForControllerResultEvent $event) {
     $page = $event->getControllerResult();
     if ($page instanceof HtmlPage) {
-      $output = theme('html_page', array('page_object' => $page));
+      $output = theme('html', array('page_object' => $page));
 
       $response = new Response((string)$output, $page->getStatusCode());
 
@@ -139,26 +139,6 @@ public function onIframeUpload(GetResponseForControllerResultEvent $event) {
   }
 
   /**
-   * Processes a successful controller into an HTTP 200 response.
-   *
-   * Some controllers may not return a response object but simply the body of
-   * one. The VIEW event is called in that case, to allow us to mutate that
-   * body into a Response object. In particular we assume that the return from
-   * an HTML-type response is a render array from a legacy page callback and
-   * render it.
-   *
-   * @param Symfony\Component\HttpKernel\Event\GetResponseForControllerResultEvent $event
-   *   The Event to process.
-   */
-  public function onHtml(GetResponseForControllerResultEvent $event) {
-    $attributes = $event->getRequest()->attributes;
-    $error = sprintf("Route is returning a render array when it shouldn't: _controller: %s, _content: %s, route: %s", $attributes->get('_controller'), $attributes->get('_content'), $attributes->get('_route'));
-    trigger_error($error, E_USER_DEPRECATED);
-    $page_callback_result = $event->getControllerResult();
-    return new Response(drupal_render_page($page_callback_result));
-  }
-
-  /**
    * Registers the methods in this class that should be listeners.
    *
    * @return array
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index 93b039d..e657681 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -312,8 +312,6 @@ function system_batch_page() {
   elseif (isset($output)) {
     // Force a page without blocks or messages to
     // display a list of collected messages later.
-    return new HtmlPage($output);
-    // @todo Figure out how to remove blocks but still render the page.
     drupal_set_page_content($output);
     $page = element_info('page');
     $page['#show_messages'] = FALSE;
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 4593efd..9f73be9 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -261,11 +261,6 @@ function system_element_info() {
   $types['page'] = array(
     '#show_messages' => TRUE,
     '#theme' => 'page',
-    '#theme_wrappers' => array('html'),
-  );
-  $types['page_body'] = array(
-    '#show_messages' => TRUE,
-    '#theme' => 'page',
   );
   // By default, we don't want Ajax commands being rendered in the context of an
   // HTML page, so we don't provide defaults for #theme or #theme_wrappers.