core/core.services.yml                             |   6 +-
 core/includes/menu.inc                             |   5 +
 .../Core/Menu/DefaultMenuLinkTreeManipulators.php  | 146 +++++++++++++
 .../Core/Menu/DefaultMenuTreeManipulators.php      | 161 --------------
 core/lib/Drupal/Core/Menu/MenuLinkTree.php         | 139 ++++--------
 .../lib/Drupal/Core/Menu/MenuLinkTreeInterface.php |  17 +-
 .../Drupal/Core/Menu/MenuParentFormSelector.php    |   7 +-
 core/modules/menu_ui/src/MenuForm.php              |  13 +-
 .../system/src/Controller/SystemController.php     |  33 ++-
 .../system/src/Plugin/Block/SystemMenuBlock.php    |   5 +
 core/modules/system/src/SystemManager.php          |   5 +
 core/modules/system/src/Tests/System/AdminTest.php |  19 +-
 core/modules/system/system.module                  |  20 +-
 .../toolbar/src/Tests/ToolbarAdminMenuTest.php     |   7 +-
 core/modules/toolbar/toolbar.module                |  74 ++++---
 .../user/src/Tests/UserAccountLinksTests.php       |   4 +
 .../Menu/DefautlMenuLinkTreeManipulatorsTest.php   | 241 +++++++++++++++++++++
 17 files changed, 565 insertions(+), 337 deletions(-)

diff --git a/core/core.services.yml b/core/core.services.yml
index 19fc8d8..cde0c05 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -266,10 +266,10 @@ services:
     arguments: ['@menu.tree_storage', '@menu_link.static.overrides', '@module_handler']
   menu.link_tree:
     class: Drupal\Core\Menu\MenuLinkTree
-    arguments: ['@menu.tree_storage', '@plugin.manager.menu.link', '@router.route_provider', '@access_manager', '@current_user', '@menu.active_trail']
+    arguments: ['@menu.tree_storage', '@plugin.manager.menu.link', '@router.route_provider', '@access_manager', '@current_user', '@menu.active_trail', '@controller_resolver']
   menu.default_tree_manipulators:
-    class: Drupal\Core\Menu\DefaultMenuTreeManipulators
-    arguments: ['@router.route_provider', '@access_manager', '@current_user']
+    class: Drupal\Core\Menu\DefaultMenuLinkTreeManipulators
+    arguments: ['@access_manager', '@current_user']
   menu.active_trail:
     class: Drupal\Core\Menu\MenuActiveTrail
     arguments: ['@plugin.manager.menu.link', '@request_stack', '@access_manager', '@current_user', '@config.factory']
diff --git a/core/includes/menu.inc b/core/includes/menu.inc
index 7ba61c2..ae269df 100644
--- a/core/includes/menu.inc
+++ b/core/includes/menu.inc
@@ -303,6 +303,11 @@ function menu_navigation_links($menu_name, $level = 0) {
   $menu_tree = \Drupal::service('menu.link_tree');
   $parameters = $menu_tree->buildPageDataTreeParameters($menu_name, $level + 1);
   $tree = $menu_tree->build($menu_name, $parameters);
+  $manipulators = array(
+    array('callable' => 'menu.default_tree_manipulators:checkAccess'),
+    array('callable' => 'menu.default_tree_manipulators:generateIndexAndSort'),
+  );
+  $tree = $menu_tree->transform($tree, $manipulators);
 
   // Go down the active trail until the right level is reached.
   while ($level-- > 0 && $tree) {
diff --git a/core/lib/Drupal/Core/Menu/DefaultMenuLinkTreeManipulators.php b/core/lib/Drupal/Core/Menu/DefaultMenuLinkTreeManipulators.php
new file mode 100644
index 0000000..2934a24
--- /dev/null
+++ b/core/lib/Drupal/Core/Menu/DefaultMenuLinkTreeManipulators.php
@@ -0,0 +1,146 @@
+<?php
+
+namespace Drupal\Core\Menu;
+
+use Drupal\Core\Access\AccessManager;
+use Drupal\Core\Session\AccountInterface;
+
+/**
+ * Provides default menu link tree manipulators.
+ */
+class DefaultMenuLinkTreeManipulators {
+
+  /**
+   * The access manager.
+   *
+   * @var \Drupal\Core\Access\AccessManager
+   */
+  protected $accessManager;
+
+  /**
+   * The current user.
+   *
+   * @var \Drupal\Core\Session\AccountInterface
+   */
+  protected $account;
+
+  /**
+   * Constructs a \Drupal\Core\Menu\DefaultMenuLinkTreeManipulators object.
+   *
+   * @param \Drupal\Core\Access\AccessManager $access_manager
+   *   The access manager.
+   * @param \Drupal\Core\Session\AccountInterface $account
+   *   The current user.
+   */
+  public function __construct(AccessManager $access_manager, AccountInterface $account) {
+    $this->accessManager = $access_manager;
+    $this->account = $account;
+  }
+
+  /**
+   * Tree manipulator that performs access checks.
+   *
+   * Removes menu items from the given menu tree whose links are inaccessible
+   * for the current user, sets the 'access' property to TRUE on tree elements
+   * that are accessible for the current user.
+   *
+   * Makes the resulting menu tree impossible to render cache, unless render
+   * caching per user is acceptable.
+   *
+   * @param array $tree
+   *   The menu tree to manipulate.
+   *
+   * @return array
+   *   The manipulated menu tree.
+   */
+  public function checkAccess(array $tree) {
+    foreach ($tree as $key => $item) {
+      // Other menu tree manipulators may already have calculated access, do
+      // not overwrite the existing value in that case.
+      if (!isset($item['access'])) {
+        $tree[$key]['access'] = $this->menuLinkCheckAccess($item['link']);
+      }
+      if ($tree[$key]['access']) {
+        if ($tree[$key]['below']) {
+          $tree[$key]['below'] = $this->checkAccess($tree[$key]['below']);
+        }
+      }
+      else {
+        unset($tree[$key]);
+      }
+    }
+    return $tree;
+  }
+
+  /**
+   * Check access for one menu link instance.
+   *
+   * @param \Drupal\Core\Menu\MenuLinkInterface $instance
+   *   The menu link instance.
+   *
+   * @return bool
+   *   TRUE if the current user can access the link, FALSE otherwise.
+   */
+  protected function menuLinkCheckAccess(MenuLinkInterface $instance) {
+    // Use the definition here since that's a lot faster than creating a Url
+    // object that we don't need.
+    $definition = $instance->getPluginDefinition();
+    // 'url' should only be populated for external links.
+    if (!empty($definition['url']) && empty($definition['route_name'])) {
+      $access = TRUE;
+    }
+    else {
+      $access = $this->accessManager->checkNamedRoute($definition['route_name'], $definition['route_parameters'], $this->account);
+    }
+    return $access;
+  }
+
+  /**
+   * Tree manipulator that generates a unique index, and sorts by it.
+   *
+   * @param array $tree
+   *   The menu tree to manipulate.
+   *
+   * @return array
+   *   The manipulated menu tree.
+   */
+  public function generateIndexAndSort(array $tree) {
+    $new_tree = array();
+    foreach ($tree as $key => $v) {
+      if ($tree[$key]['below']) {
+        $tree[$key]['below'] = $this->generateIndexAndSort($tree[$key]['below']);
+      }
+      /** @var \Drupal\Core\Menu\MenuLinkInterface $instance */
+      $instance = $tree[$key]['link'];
+      // The weights are made a uniform 5 digits by adding 50000 as an offset.
+      // After $this->menuLinkCheckAccess(), $instance->getTitle() has the
+      // localized or translated title. Adding the plugin id to the end of the
+      // index insures that it is unique.    }
+      $new_tree[(50000 + $instance->getWeight()) . ' ' . $instance->getTitle() . ' ' . $instance->getPluginId()] = $tree[$key];
+    }
+    ksort($new_tree);
+    return $new_tree;
+  }
+
+  /**
+   * Tree manipulator that flattens the tree to a single level.
+   *
+   * @param array $tree
+   *   The menu tree to manipulate.
+   *
+   * @return array
+   *   The manipulated menu tree.
+   */
+  public function flatten($tree) {
+    foreach ($tree as $key => $item) {
+      if ($tree[$key]['below']) {
+        $tree[$key]['below'] = $this->flatten($tree[$key]['below']);
+        foreach ($tree[$key]['below'] as $child_key => $child_item) {
+          $tree[$child_key] = $child_item;
+        }
+      }
+    }
+    return $tree;
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Menu/DefaultMenuTreeManipulators.php b/core/lib/Drupal/Core/Menu/DefaultMenuTreeManipulators.php
deleted file mode 100644
index c909ac7..0000000
--- a/core/lib/Drupal/Core/Menu/DefaultMenuTreeManipulators.php
+++ /dev/null
@@ -1,161 +0,0 @@
-<?php
-
-namespace Drupal\Core\Menu;
-
-use Drupal\Core\Access\AccessManager;
-use Drupal\Core\Routing\RouteProviderInterface;
-use Drupal\Core\Session\AccountInterface;
-
-class DefaultMenuTreeManipulators {
-
-  /**
-   * The route provider to load routes by name.
-   *
-   * @var \Drupal\Core\Routing\RouteProviderInterface
-   */
-  protected $routeProvider;
-
-  /**
-   * The access manager.
-   *
-   * @var \Drupal\Core\Access\AccessManager
-   */
-  protected $accessManager;
-
-  /**
-   * The current user.
-   *
-   * @var \Drupal\Core\Session\AccountInterface
-   */
-  protected $account;
-
-  /**
-   * Constructs a \Drupal\Core\Menu\DefaultMenuTreeManipulators object.
-   *
-   * @param \Drupal\Core\Routing\RouteProviderInterface $route_provider
-   *   The route provider to load routes by name.
-   * @param \Drupal\Core\Access\AccessManager $access_manager
-   *   The access manager.
-   * @param \Drupal\Core\Session\AccountInterface $account
-   *   The current user.
-   */
-  public function __construct(RouteProviderInterface $route_provider, AccessManager $access_manager, AccountInterface $account) {
-    $this->routeProvider = $route_provider;
-    $this->accessManager = $access_manager;
-    $this->account = $account;
-  }
-
-  /**
-   * Tree manipulator that performs access checks.
-   *
-   * Removes menu items from the given menu tree whose links are inaccessible
-   * for the current user, sets the 'access' property to TRUE on tree elements
-   * that are accessible for the current user.
-   *
-   * Makes the resulting menu tree impossible to render cache, unless render
-   * caching per user is acceptable.
-   *
-   * @param array $tree
-   *   The menu tree to manipulate.
-   *
-   * @return array
-   *   The manipulated menu tree.
-   */
-  public function checkAccess(array $tree) {
-    $this->doTreeCheckAccess($tree);
-    return $tree;
-  }
-
-  /**
-   * Helper function that recursively checks access for each item.
-   */
-  protected function doTreeCheckAccess(&$tree) {
-    foreach ($tree as $key => $item) {
-      // Other menu tree manipulators may already have calculated access, do
-      // not overwrite the existing value in that case.
-      if (!isset($item['access'])) {
-        $tree[$key]['access'] = $this->menuLinkCheckAccess($item['link']);
-      }
-      if ($tree[$key]['access']) {
-        if ($tree[$key]['below']) {
-          $this->doTreeCheckAccess($tree[$key]['below']);
-        }
-      }
-      else {
-        unset($tree[$key]);
-      }
-    }
-  }
-
-  /**
-   * Check access for one menu link instance.
-   *
-   * @param \Drupal\Core\Menu\MenuLinkInterface $instance
-   *   The menu link instance.
-   *
-   * @return bool
-   *   TRUE if the current user can access the link, FALSE otherwise.
-   */
-  protected function menuLinkCheckAccess(MenuLinkInterface $instance) {
-    // Use the definition here since that's a lot faster than creating a Url
-    // object that we don't need.
-    $definition = $instance->getPluginDefinition();
-    // 'url' should only be populated for external links.
-    if (!empty($definition['url']) && empty($definition['route_name'])) {
-      $access = TRUE;
-    }
-    else {
-      $access = $this->accessManager->checkNamedRoute($definition['route_name'], $definition['route_parameters'], $this->account);
-    }
-    return $access;
-  }
-
-  /**
-   * Tree manipulator that generates a unique index, and sorts by it.
-   *
-   * @param array $tree
-   *   The menu tree to manipulate.
-   *
-   * @return array
-   *   The manipulated menu tree.
-   */
-  public function generateIndexAndSort(array $tree) {
-    $new_tree = array();
-    foreach ($tree as $key => $v) {
-      if ($tree[$key]['below']) {
-        $tree[$key]['below'] = $this->generateIndexAndSort($tree[$key]['below']);
-      }
-      /** @var \Drupal\Core\Menu\MenuLinkInterface $instance */
-      $instance = $tree[$key]['link'];
-      // The weights are made a uniform 5 digits by adding 50000 as an offset.
-      // After $this->menuLinkCheckAccess(), $instance->getTitle() has the
-      // localized or translated title. Adding the plugin id to the end of the
-      // index insures that it is unique.    }
-      $new_tree[(50000 + $instance->getWeight()) . ' ' . $instance->getTitle() . ' ' . $instance->getPluginId()] = $tree[$key];
-    }
-    ksort($new_tree);
-    return $new_tree;
-  }
-
-  /**
-   * Tree manipulator that flattens the tree to a single level.
-   *
-   * @param array $tree
-   *   The menu tree to manipulate.
-   *
-   * @return array
-   *   The manipulated menu tree.
-   */
-  public function flatten($tree) {
-    foreach ($tree as $key => $item) {
-      if ($tree[$key]['below']) {
-        $tree[$key]['below'] = $this->flatten($tree[$key]['below']);
-        foreach ($tree[$key]['below'] as $child_key => $child_item) {
-          $tree[$child_key] = $child_item;
-        }
-      }
-    }
-    return $tree;
-  }
-
-}
\ No newline at end of file
diff --git a/core/lib/Drupal/Core/Menu/MenuLinkTree.php b/core/lib/Drupal/Core/Menu/MenuLinkTree.php
index 6994452..1cbf233 100644
--- a/core/lib/Drupal/Core/Menu/MenuLinkTree.php
+++ b/core/lib/Drupal/Core/Menu/MenuLinkTree.php
@@ -7,9 +7,12 @@
 
 namespace Drupal\Core\Menu;
 
+use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Access\AccessManager;
+use Drupal\Core\Controller\ControllerResolverInterface;
 use Drupal\Core\Routing\RouteProviderInterface;
 use Drupal\Core\Session\AccountInterface;
+use Symfony\Component\DependencyInjection\Tests\Compiler\InlineServiceDefinitionsPassTest;
 
 /**
  * Manages discovery, instantiation, and tree building of menu link plugins.
@@ -61,6 +64,13 @@ class MenuLinkTree implements MenuLinkTreeInterface {
   protected $menuActiveTrail;
 
   /**
+   * The controller resolver.
+   *
+   * @var \Drupal\Core\Controller\ControllerResolverInterface
+   */
+  protected $controllerResolver;
+
+  /**
    * Constructs a \Drupal\Core\Menu\MenuLinkTree object.
    *
    * @param \Drupal\Core\Menu\MenuTreeStorageInterface $tree_storage
@@ -75,14 +85,17 @@ class MenuLinkTree implements MenuLinkTreeInterface {
    *   The current user.
    * @param \Drupal\Core\Menu\MenuActiveTrailInterface $menu_active_trail
    *   The active menu trail service.
+   * @param \Drupal\Core\Controller\ControllerResolverInterface $controller_resolver
+   *   The controller resolver.
    */
-  public function __construct(MenuTreeStorageInterface $tree_storage, MenuLinkManagerInterface $menu_link_manager, RouteProviderInterface $route_provider, AccessManager $access_manager, AccountInterface $account, MenuActiveTrailInterface $menu_active_trail) {
+  public function __construct(MenuTreeStorageInterface $tree_storage, MenuLinkManagerInterface $menu_link_manager, RouteProviderInterface $route_provider, AccessManager $access_manager, AccountInterface $account, MenuActiveTrailInterface $menu_active_trail, ControllerResolverInterface $controller_resolver) {
     $this->treeStorage = $tree_storage;
     $this->menuLinkManager = $menu_link_manager;
     $this->routeProvider = $route_provider;
     $this->accessManager = $access_manager;
     $this->account = $account;
     $this->menuActiveTrail = $menu_active_trail;
+    $this->controllerResolver = $controller_resolver;
   }
 
   /**
@@ -135,6 +148,9 @@ public function render($tree) {
       $element['#title'] = $link->getTitle();
       $element['#url'] = $link->getUrlObject();
       $element['#below'] = $data['below'] ? $this->render($data['below']) : array();
+      if (isset($data['options'])) {
+        $element['#url']->setOptions(NestedArray::mergeDeep($element['#url']->getOptions(), $data['options']));
+      }
       $element['#original_link'] = $link;
       // Index using the link's unique ID.
       $build[$link->getPluginId()] = $element;
@@ -215,37 +231,16 @@ public function buildAllDataTreeParameters($id = NULL, $max_depth = NULL) {
   /**
    * {@inheritdoc}
    */
-  public function getChildLinks($id, $max_relative_depth = NULL) {
-    $links = array();
-    $definitions = $this->treeStorage->loadAllChildLinks($id, $max_relative_depth);
-    foreach ($definitions as $id => $definition) {
-      $access = $this->menuLinkCheckAccess($definition);
-      if ($access) {
-        $links[$id] = $this->menuLinkManager->createInstance($definition['id']);;
-      }
-    }
-    return $links;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function buildSubtree($id, $max_relative_depth = NULL) {
     $data = $this->treeStorage->loadSubtreeData($id, $max_relative_depth);
     if ($data['subtree']) {
-      $subtree = $data['subtree'];
-      // Check access and instantiate.
-      $access = $this->menuLinkCheckAccess($subtree['definition']);
-      if ($access) {
-        $subtree['link'] = $this->menuLinkManager->createInstance($subtree['definition']['id']);
-        // Pre-load all the route objects in the tree for access checks.
-        if ($data['route_names']) {
-          $this->routeProvider->getRoutesByNames($data['route_names']);
-        }
-        $this->createInstances($subtree['below']);
-        $this->treeCheckAccess($subtree['below']);
-        return $subtree;
+      // Pre-load all the route objects in the subtree for access checks.
+      if ($data['route_names']) {
+        $this->routeProvider->getRoutesByNames($data['route_names']);
       }
+      $tree = array($data['subtree']['definition']['id'] => $data['subtree']);
+      $this->createInstances($tree);
+      return $tree;
     }
     return NULL;
   }
@@ -261,19 +256,27 @@ public function build($menu_name, array $parameters = array()) {
     }
     $tree = $data['tree'];
     $this->createInstances($tree);
-    $this->treeCheckAccess($tree);
     return $tree;
   }
 
   /**
-   * Sorts the menu tree and recursively checks access for each item.
-   *
-   * @param array $tree
-   *   The menu tree you wish to operate on.
+   * {@inheritdoc}
    */
-  protected function treeCheckAccess(&$tree) {
-    $this->doTreeCheckAccess($tree);
-    $this->sortTree($tree);
+  public function transform(array $tree, array $manipulators) {
+    foreach ($manipulators as $manipulator) {
+      // Prepare the arguments for the menu tree manipulator callable; the first
+      // argument is always the menu link tree.
+      $args = isset($manipulator['args']) ? $manipulator['args'] : array();
+      array_unshift($args, $tree);
+
+      $callable = $manipulator['callable'];
+      if (strpos($callable, '::') === FALSE) {
+        $callable = $this->controllerResolver->getControllerFromDefinition($callable);
+      }
+
+      $tree = call_user_func_array($callable, $args);
+    }
+    return $tree;
   }
 
   /**
@@ -285,70 +288,8 @@ protected function createInstances(&$tree) {
         $this->createInstances($tree[$key]['below']);
       }
       $tree[$key]['link'] = $this->menuLinkManager->createInstance($tree[$key]['definition']['id']);
+      unset($tree[$key]['definition']);
     }
   }
 
-  /**
-   * Helper function that recursively checks access for each item.
-   */
-  protected function doTreeCheckAccess(&$tree) {
-    foreach ($tree as $key => $v) {
-      $definition = $tree[$key]['definition'];
-      $tree[$key]['access'] = $this->menuLinkCheckAccess($definition);
-      if ($tree[$key]['access']) {
-        if ($tree[$key]['below']) {
-          $this->doTreeCheckAccess($tree[$key]['below']);
-        }
-        unset($tree[$key]['definition']);
-      }
-      else {
-        unset($tree[$key]);
-      }
-    }
-  }
-
-  /**
-   * Sorts the menu tree and recursively using the weight and title.
-   *
-   * @param array $tree
-   *   The menu tree you wish to operate on.
-   */
-  protected function sortTree(&$tree) {
-    $new_tree = array();
-    foreach ($tree as $key => $v) {
-      if ($tree[$key]['below']) {
-        $this->sortTree($tree[$key]['below']);
-      }
-      $instance = $tree[$key]['link'];
-      // The weights are made a uniform 5 digits by adding 50000 as an offset.
-      // After $this->menuLinkCheckAccess(), $instance->getTitle() has the
-      // localized or translated title. Adding the plugin id to the end of the
-      // index insures that it is unique.
-      $new_tree[(50000 + $instance->getWeight()) . ' ' . $instance->getTitle() . ' ' . $instance->getPluginId()] = $tree[$key];
-    }
-    // Sort siblings in the tree based on the weights and localized titles.
-    ksort($new_tree);
-    $tree = $new_tree;
-  }
-
-  /**
-   * Check access for the item and create an instance if it is accessible.
-   *
-   * @param array $definition
-   *   The menu link definition.
-   *
-   * @return \Drupal\Core\Menu\MenuLinkInterface|NULL
-   *   A plugin instance or NULL if the current user can not access its route.
-   */
-  protected function menuLinkCheckAccess(array $definition) {
-    // 'url' should only be populated for external links.
-    if (!empty($definition['url']) && empty($definition['route_name'])) {
-      $access = TRUE;
-    }
-    else {
-      $access = $this->accessManager->checkNamedRoute($definition['route_name'], $definition['route_parameters'], $this->account);
-    }
-    return $access;
-  }
-
 }
diff --git a/core/lib/Drupal/Core/Menu/MenuLinkTreeInterface.php b/core/lib/Drupal/Core/Menu/MenuLinkTreeInterface.php
index 92c03d3..e3c2851 100644
--- a/core/lib/Drupal/Core/Menu/MenuLinkTreeInterface.php
+++ b/core/lib/Drupal/Core/Menu/MenuLinkTreeInterface.php
@@ -146,17 +146,16 @@ public function build($menu_name, array $parameters = array());
   public function buildSubtree($id, $max_relative_depth = NULL);
 
   /**
-   * Loads all child links of a given menu link.
+   * Applies the given tree manipulators in order to a menu link tree.
    *
-   * @param string $id
-   *   The menu link plugin ID.
-   *
-   * @param int $max_relative_depth
-   *   If provided, limit the maximum relative depth of children retrieved.
+   * @param array $tree
+   *   The menu tree to manipulate.
+   * @param array $manipulators
+   *   The menu tree manipulators to apply.
    *
-   * @return \Drupal\Core\Menu\MenuLinkInterface[]
-   *   An array of child links keyed by ID.
+   * @return array
+   *   The manipulated menu tree.
    */
-  public function getChildLinks($id, $max_relative_depth = NULL);
+  public function transform(array $tree, array $manipulators);
 
 }
diff --git a/core/lib/Drupal/Core/Menu/MenuParentFormSelector.php b/core/lib/Drupal/Core/Menu/MenuParentFormSelector.php
index b0fd804..b6ee9d8 100644
--- a/core/lib/Drupal/Core/Menu/MenuParentFormSelector.php
+++ b/core/lib/Drupal/Core/Menu/MenuParentFormSelector.php
@@ -14,7 +14,7 @@
 class MenuParentFormSelector implements MenuParentFormSelectorInterface {
 
   /**
-   * The menu link tree storage.
+   * The menu link tree service.
    *
    * @var \Drupal\Core\Menu\MenuLinkTreeInterface
    */
@@ -47,6 +47,11 @@ public function getParentSelectOptions($id = '', array $menus = NULL) {
 
       $parameters = $this->menuLinkTree->buildAllDataTreeParameters(NULL, $depth_limit);
       $tree = $this->menuLinkTree->build($menu_name, $parameters);
+      $manipulators = array(
+        array('callable' => 'menu.default_tree_manipulators:checkAccess'),
+        array('callable' => 'menu.default_tree_manipulators:generateIndexAndSort'),
+      );
+      $tree = $this->menuLinkTree->transform($tree, $manipulators);
       $this->parentSelectOptionsTreeWalk($tree, $menu_name, '--', $options, $id, $depth_limit);
     }
     return $options;
diff --git a/core/modules/menu_ui/src/MenuForm.php b/core/modules/menu_ui/src/MenuForm.php
index d73fca2..2512bbe 100644
--- a/core/modules/menu_ui/src/MenuForm.php
+++ b/core/modules/menu_ui/src/MenuForm.php
@@ -214,17 +214,22 @@ protected function buildOverviewForm(array &$form, array &$form_state) {
     $form_state += array('menu_overview_form_parents' => array());
 
     $form['#attached']['css'] = array(drupal_get_path('module', 'menu') . '/css/menu.admin.css');
-    // We indicate that a menu administrator is running the menu access check.
-    $this->getRequest()->attributes->set('_menu_admin', TRUE);
 
     $parameters = $this->menuTree->buildAllDataTreeParameters();
     $tree = $this->menuTree->build($this->entity->id(), $parameters);
 
+    // We indicate that a menu administrator is running the menu access check.
+    $manipulators = array(
+      array('callable' => 'menu.default_tree_manipulators:checkAccess'),
+      array('callable' => 'menu.default_tree_manipulators:generateIndexAndSort'),
+    );
+    $this->getRequest()->attributes->set('_menu_admin', TRUE);
+    $tree = $this->menuTree->transform($tree, $manipulators);
+    $this->getRequest()->attributes->set('_menu_admin', FALSE);
+
     $count = $this->countElements($tree);
     $delta = max($count, 50);
 
-    $this->getRequest()->attributes->set('_menu_admin', FALSE);
-
     $form = array_merge($form, $this->buildOverviewTreeForm($tree, $delta));
     $form['#empty_text'] = $this->t('There are no menu links yet. <a href="@link">Add link</a>.', array('@link' => url('admin/structure/menu/manage/' . $this->entity->id() .'/add')));
 
diff --git a/core/modules/system/src/Controller/SystemController.php b/core/modules/system/src/Controller/SystemController.php
index 09fc577..61fe270 100644
--- a/core/modules/system/src/Controller/SystemController.php
+++ b/core/modules/system/src/Controller/SystemController.php
@@ -7,12 +7,12 @@
 
 namespace Drupal\system\Controller;
 
-use Drupal\Core\Menu\MenuLinkInterface;
 use Drupal\Component\Serialization\Json;
 use Drupal\Core\Controller\ControllerBase;
 use Drupal\Core\Entity\Query\QueryFactory;
 use Drupal\Core\Extension\ThemeHandlerInterface;
 use Drupal\Core\Form\FormBuilderInterface;
+use Drupal\Core\Menu\MenuLinkTreeInterface;
 use Drupal\Core\Theme\ThemeAccessCheck;
 use Drupal\system\SystemManager;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -58,6 +58,13 @@ class SystemController extends ControllerBase {
   protected $themeHandler;
 
   /**
+   * The menu link tree service.
+   *
+   * @var \Drupal\Core\Menu\MenuLinkTreeInterface
+   */
+  protected $menuLinkTree;
+
+  /**
    * Constructs a new SystemController.
    *
    * @param \Drupal\system\SystemManager $systemManager
@@ -70,13 +77,16 @@ class SystemController extends ControllerBase {
    *   The form builder.
    * @param \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler
    *   The theme handler.
+   * @param \Drupal\Core\Menu\MenuLinkTreeInterface
+   *   The menu link tree service.
    */
-  public function __construct(SystemManager $systemManager, QueryFactory $queryFactory, ThemeAccessCheck $theme_access, FormBuilderInterface $form_builder, ThemeHandlerInterface $theme_handler) {
+  public function __construct(SystemManager $systemManager, QueryFactory $queryFactory, ThemeAccessCheck $theme_access, FormBuilderInterface $form_builder, ThemeHandlerInterface $theme_handler, MenuLinkTreeInterface $menu_link_tree) {
     $this->systemManager = $systemManager;
     $this->queryFactory = $queryFactory;
     $this->themeAccess = $theme_access;
     $this->formBuilder = $form_builder;
     $this->themeHandler = $theme_handler;
+    $this->menuLinkTree = $menu_link_tree;
   }
 
   /**
@@ -88,7 +98,8 @@ public static function create(ContainerInterface $container) {
       $container->get('entity.query'),
       $container->get('access_check.theme'),
       $container->get('form_builder'),
-      $container->get('theme_handler')
+      $container->get('theme_handler'),
+      $container->get('menu.link_tree')
     );
   }
 
@@ -106,15 +117,13 @@ public function overview($link_id) {
     if ($this->systemManager->checkRequirements() && $this->currentUser()->hasPermission('administer site configuration')) {
       drupal_set_message($this->t('One or more problems were detected with your Drupal installation. Check the <a href="@status">status report</a> for more information.', array('@status' => url('admin/reports/status'))), 'error');
     }
-    /* @var \Drupal\Core\Menu\MenuLinkTreeInterface $menu_tree */
-    $menu_tree = \Drupal::menuTree();
-    //$system_link = $menu_tree->createInstance($link_id); // 'system.admin_config'
-    // Only find the children of this link.
-    //$parameters['expanded'][] = 'system.admin_config';
-    //$parameters['conditions']['hidden'] = 0;
-    //$tree =  $menu_tree->buildTree($system_link->getMenuName(), $parameters);
-    $top_tree = $menu_tree->buildSubtree($link_id, 1);
-    $tree = !empty($top_tree['below']) ? $top_tree['below'] : array();
+    $top_tree = $this->menuLinkTree->buildSubtree($link_id, 1);
+    $tree = !empty($top_tree[$link_id]['below']) ? $top_tree[$link_id]['below'] : array();
+    $manipulators = array(
+      array('callable' => 'menu.default_tree_manipulators:checkAccess'),
+      array('callable' => 'menu.default_tree_manipulators:generateIndexAndSort'),
+    );
+    $tree = $this->menuLinkTree->transform($tree, $manipulators);
     $blocks = array();
     // Load all menu links below it.
     foreach ($tree as $key => $item) {
diff --git a/core/modules/system/src/Plugin/Block/SystemMenuBlock.php b/core/modules/system/src/Plugin/Block/SystemMenuBlock.php
index 9716dd8..e6fdd7c 100644
--- a/core/modules/system/src/Plugin/Block/SystemMenuBlock.php
+++ b/core/modules/system/src/Plugin/Block/SystemMenuBlock.php
@@ -81,6 +81,11 @@ public function build() {
     $menu_name = $this->getDerivativeId();
     $parameters = $this->menuTree->buildPageDataTreeParameters($menu_name);
     $tree = $this->menuTree->build($menu_name, $parameters);
+    $manipulators = array(
+      array('callable' => 'menu.default_tree_manipulators:checkAccess'),
+      array('callable' => 'menu.default_tree_manipulators:generateIndexAndSort'),
+    );
+    $tree = $this->menuTree->transform($tree, $manipulators);
     return $this->menuTree->render($tree);
   }
 
diff --git a/core/modules/system/src/SystemManager.php b/core/modules/system/src/SystemManager.php
index 2e09e49..98b3071 100644
--- a/core/modules/system/src/SystemManager.php
+++ b/core/modules/system/src/SystemManager.php
@@ -219,6 +219,11 @@ public function getAdminBlock(MenuLinkInterface $instance) {
     $parameters['expanded'][] = $instance->getPluginId();
     $parameters['conditions']['hidden'] = 0;
     $tree =  $this->menuTree->build($instance->getMenuName(), $parameters);
+    $manipulators = array(
+      array('callable' => 'menu.default_tree_manipulators:checkAccess'),
+      array('callable' => 'menu.default_tree_manipulators:generateIndexAndSort'),
+    );
+    $tree = $this->menuTree->transform($tree, $manipulators);
     foreach ($tree as $key => $item) {
       /** @var $link \Drupal\Core\Menu\MenuLinkInterface */
       $link = $item['link'];
diff --git a/core/modules/system/src/Tests/System/AdminTest.php b/core/modules/system/src/Tests/System/AdminTest.php
index 04543db..3a15495 100644
--- a/core/modules/system/src/Tests/System/AdminTest.php
+++ b/core/modules/system/src/Tests/System/AdminTest.php
@@ -131,9 +131,24 @@ function testAdminPages() {
   protected function getTopLevelMenuLinks() {
     /** @var \Drupal\Core\Menu\MenuLinkTreeInterface $menu_tree */
     $menu_tree = $this->container->get('menu.link_tree');
+
     // The system.admin link is normally the parent of all top-level admin links.
-    $menu_items = $menu_tree->getChildLinks('system.admin', 1);
-    return $menu_items;
+    $link_id = 'system.admin';
+    $top_tree = $menu_tree->buildSubtree($link_id, 1);
+    $tree = !empty($top_tree[$link_id]['below']) ? $top_tree[$link_id]['below'] : array();
+    $manipulators = array(
+      array('callable' => 'menu.default_tree_manipulators:checkAccess'),
+      array('callable' => 'menu.default_tree_manipulators:flatten'),
+    );
+    $tree = $menu_tree->transform($tree, $manipulators);
+
+    // Transform the tree to a list of menu links.
+    $menu_links = array();
+    foreach ($tree as $item) {
+      $menu_links[] = $item['link'];
+    }
+
+    return $menu_links;
   }
 
   /**
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 1e6bffa..9fd85f4 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -1454,24 +1454,28 @@ function system_admin_compact_mode() {
  *   An array of task links.
  */
 function system_get_module_admin_tasks($module, array $info) {
-  $links = &drupal_static(__FUNCTION__);
+  $tree = &drupal_static(__FUNCTION__);
 
   /* @var \Drupal\Core\Menu\MenuLinkTreeInterface $menu_tree */
   $menu_tree = \Drupal::service('menu.link_tree');
 
-  if (!isset($links)) {
-    $links = array();
-    /* @var \Drupal\Core\Menu\MenuLinkInterface $admin_link */
-    $links = $menu_tree->getChildLinks('system.admin');
+  if (!isset($tree)) {
+    $tree = $menu_tree->buildSubtree('system.admin');
+    $manipulators = array(
+      array('callable' => 'menu.default_tree_manipulators:checkAccess'),
+      array('callable' => 'menu.default_tree_manipulators:generateIndexAndSort'),
+      array('callable' => 'menu.default_tree_manipulators:flatten'),
+    );
+    $tree = $menu_tree->transform($tree, $manipulators);
   }
 
   $admin_tasks = array();
-  $titles = array();
-  foreach ($links as $id => $instance) {
+  foreach ($tree as $item) {
+    $instance = $item['link'];
     if ($instance->getProvider() != $module) {
       continue;
     }
-    $admin_tasks[$id] = array(
+    $admin_tasks[] = array(
       'title' => $instance->getTitle(),
       'description' => $instance->getDescription(),
       'url' => $instance->getUrlObject(),
diff --git a/core/modules/toolbar/src/Tests/ToolbarAdminMenuTest.php b/core/modules/toolbar/src/Tests/ToolbarAdminMenuTest.php
index 4f8d90c..627e164 100644
--- a/core/modules/toolbar/src/Tests/ToolbarAdminMenuTest.php
+++ b/core/modules/toolbar/src/Tests/ToolbarAdminMenuTest.php
@@ -133,14 +133,13 @@ function testModuleStatusChangeSubtreesHashCacheClear() {
    * Tests toolbar cache tags implementation.
    */
   function testMenuLinkUpdateSubtreesHashCacheClear() {
-    $links = \Drupal::menuTree()->getChildLinks('system.admin', 2);
-    $links = array_values($links);
-    $link = array_shift($links);
+    // The ID of a (any) admin menu link.
+    $admin_menu_link_id = 'system.admin_config_development';
 
     // Disable the link.
     $edit = array();
     $edit['enabled'] = FALSE;
-    $this->drupalPostForm("admin/structure/menu/link/" . $link->getPluginId() . "/edit", $edit, t('Save'));
+    $this->drupalPostForm("admin/structure/menu/link/" . $admin_menu_link_id . "/edit", $edit, t('Save'));
     $this->assertResponse(200);
     $this->assertText('The menu link has been saved.');
 
diff --git a/core/modules/toolbar/toolbar.module b/core/modules/toolbar/toolbar.module
index 59753c5..c760871 100644
--- a/core/modules/toolbar/toolbar.module
+++ b/core/modules/toolbar/toolbar.module
@@ -348,13 +348,17 @@ function toolbar_toolbar() {
 
   $menu_tree = \Drupal::menuTree();
   // Retrieve the administration menu from the menu tree manager.
-  $tree = $menu_tree->build('admin', array(
+  $parameters = array(
     'expanded' => array('system.admin')
-  ));
-
+  );
+  $tree = $menu_tree->build('admin', $parameters);
+  $manipulators = array(
+    array('callable' => 'menu.default_tree_manipulators:checkAccess'),
+    array('callable' => 'menu.default_tree_manipulators:generateIndexAndSort'),
+    array('callable' => 'toolbar_menu_navigation_links'),
+  );
+  $tree = $menu_tree->transform($tree, $manipulators);
   $render_tree = $menu_tree->render($tree);
-  // Add attributes to the links before rendering.
-  toolbar_menu_navigation_links($render_tree);
 
   $menu = array(
     '#heading' => t('Administration menu'),
@@ -408,45 +412,41 @@ function toolbar_toolbar() {
 }
 
 /**
- * Modifies a render array of links from a menu tree array.
+ * Tree manipulator that adds toolbar-specific attributes.
  *
- * Adds route-based IDs and icon placeholders to the link attributes.
+ * @param array $tree
+ *   The menu tree to manipulate.
  *
- * @param array $render_tree
- *   A menu link tree render array. The contained url objects are modified.
+ * @return array
+ *   The manipulated menu tree.
  */
-function toolbar_menu_navigation_links($render_tree) {
-  foreach (Element::children($render_tree, FALSE) as $key) {
-    $element = $render_tree[$key];
-    // Configure sub-items.
-    if (!empty($element['#below'])) {
-      toolbar_menu_navigation_links($render_tree[$key]['#below']);
+function toolbar_menu_navigation_links($tree) {
+  foreach ($tree as $key => $item) {
+    if (!empty($item['below'])) {
+      toolbar_menu_navigation_links($tree[$key]['below']);
     }
-    /** @var \Drupal\Core\Url $url */
-    $url = $element['#url'];
+
     // Make sure we have a path specific ID in place, so we can attach icons
-    // and behaviors to the items.
+    // and behaviors to the menu links.
+    $link = $item['link'];
+    $url = $link->getUrlObject();
     if ($url->isExternal()) {
-      // This is an unusual case, so just get a distinct, safe string
+      // This is an unusual case, so just get a distinct, safe string.
       $id = substr(Crypt::hashBase64($url->getPath()), 0, 16);
     }
     else {
       $id = str_replace(array('.', '<', '>'), array('-', '', ''), $url->getRouteName());
     }
-    $options = $url->getOptions();
-    $options['attributes'] = array(
-      'id' => 'toolbar-link-' . $id,
-      'class' => array(
-        'toolbar-icon',
-      ),
-    );
+
     // Get the non-localized title to make the icon class.
-    $definition = $element['#original_link']->getPluginDefinition();
-    if (!empty($definition['title'])) {
-      $options['attributes']['class'][] = 'toolbar-icon-' . strtolower(str_replace(' ', '-', $definition['title']));
-    }
-    $url->setOptions($options);
+    $definition = $link->getPluginDefinition();
+
+    $tree[$key]['options']['attributes']['id'] = 'toolbar-link-' . $id;
+    $tree[$key]['options']['attributes']['class'][] = 'toolbar-icon';
+    $tree[$key]['options']['attributes']['class'][] = 'toolbar-icon-' . strtolower(str_replace(' ', '-', $definition['title']));
+    $tree[$key]['options']['attributes']['title'] = String::checkPlain($link->getDescription());
   }
+  return $tree;
 }
 
 /**
@@ -455,15 +455,21 @@ function toolbar_menu_navigation_links($render_tree) {
 function toolbar_get_rendered_subtrees() {
   /** @var \Drupal\Core\Menu\MenuLinkTreeInterface $menu_tree */
   $menu_tree = \Drupal::service('menu.link_tree');
-  $top_tree = $menu_tree->buildSubtree('system.admin', 3);
-  $tree = !empty($top_tree['below']) ? $top_tree['below'] : array();
+  $link_id = 'system.admin';
+  $top_tree = $menu_tree->buildSubtree($link_id, 3);
+  $tree = !empty($top_tree[$link_id]['below']) ? $top_tree[$link_id]['below'] : array();
+  $manipulators = array(
+    array('callable' => 'menu.default_tree_manipulators:checkAccess'),
+    array('callable' => 'menu.default_tree_manipulators:generateIndexAndSort'),
+    array('callable' => 'toolbar_menu_navigation_links'),
+  );
+  $tree = $menu_tree->transform($tree, $manipulators);
   $subtrees = array();
   foreach ($tree as $tree_item) {
     /** @var \Drupal\Core\Menu\MenuLinkInterface $item */
     $item = $tree_item['link'];
     if ($tree_item['below']) {
       $subtree = $menu_tree->render($tree_item['below']);
-      toolbar_menu_navigation_links($subtree);
       $output = drupal_render($subtree);
     }
     else {
diff --git a/core/modules/user/src/Tests/UserAccountLinksTests.php b/core/modules/user/src/Tests/UserAccountLinksTests.php
index c472b4b..ee529e9 100644
--- a/core/modules/user/src/Tests/UserAccountLinksTests.php
+++ b/core/modules/user/src/Tests/UserAccountLinksTests.php
@@ -70,6 +70,10 @@ function testSecondaryMenu() {
     /** @var \Drupal\Core\Menu\MenuLinkTreeInterface $menu_tree */
     $menu_tree = \Drupal::service('menu.link_tree');
     $tree = $menu_tree->build('account');
+    $manipulators = array(
+      array('callable' => 'menu.default_tree_manipulators:checkAccess'),
+    );
+    $tree = $menu_tree->transform($tree, $manipulators);
     $this->assertEqual(count($tree), 1, 'The secondary links menu contains only one menu link.');
     $link = reset($tree);
     $link = $link['link'];
diff --git a/core/tests/Drupal/Tests/Core/Menu/DefautlMenuLinkTreeManipulatorsTest.php b/core/tests/Drupal/Tests/Core/Menu/DefautlMenuLinkTreeManipulatorsTest.php
new file mode 100644
index 0000000..c14ce7f
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Menu/DefautlMenuLinkTreeManipulatorsTest.php
@@ -0,0 +1,241 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\menu_link\Tests\DefaultMenuTreeManipulatorsTest.
+ */
+
+namespace Drupal\Tests\Core\Menu;
+
+use Drupal\Core\Menu\DefaultMenuLinkTreeManipulators;
+use Drupal\Core\Menu\MenuLinkDefault;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Tests the default menu link tree manipulators.
+ *
+ * @group Drupal
+ * @group Menu
+ *
+ * @coversDefaultClass \Drupal\Core\Menu\DefaultMenuLinkTreeManipulators
+ */
+class DefaultMenuLinkTreeManipulatorsTest extends UnitTestCase {
+
+  /**
+   * The mocked access manager.
+   *
+   * @var \Drupal\Core\Access\AccessManager|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $accessManager;
+
+  /**
+   * The mocked current user.
+   *
+   * @var \Drupal\Core\Session\AccountInterface|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $currentUser;
+
+  /**
+   * The default menu link tree manipulators.
+   *
+   * @var \Drupal\Core\Menu\DefaultMenuLinkTreeManipulators
+   */
+  protected $defaultMenuTreeManipulators;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getInfo() {
+    return array(
+      'name' => 'Tests \Drupal\Core\Menu\DefaultMenuLinkTreeManipulators',
+      'description' => '',
+      'group' => 'Menu',
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    $this->accessManager = $this->getMockBuilder('\Drupal\Core\Access\AccessManager')
+      ->disableOriginalConstructor()->getMock();
+    $this->currentUser = $this->getMock('Drupal\Core\Session\AccountInterface');
+
+    $this->defaultMenuTreeManipulators = new DefaultMenuLinkTreeManipulators($this->accessManager, $this->currentUser);
+  }
+
+  /**
+   * Mock a menu link.
+   *
+   * @param array $definition
+   *   A menu link definition.
+   *
+   * @return \Drupal\Core\Menu\MenuLinkDefault
+   *   The menu link instance.
+   */
+  protected function mockLink(array $definition) {
+    $container = $this->getMock('Symfony\Component\DependencyInjection\ContainerInterface');
+    $container->expects($this->any())
+      ->method('get')
+      ->with('menu_link.static.overrides')
+      ->will($this->returnValue($this->getMock('\Drupal\Core\Menu\StaticMenuLinkOverridesInterface')));
+
+    $string_translation = $this->getMock('\Drupal\Core\StringTranslation\TranslationInterface');
+    $string_translation->expects($this->any())
+      ->method('translate')
+      ->will($this->returnArgument(0));
+
+    $defaults = array (
+      'menu_name' => 'admin',
+      'route_name' => 'MUST BE PROVIDED',
+      'route_parameters' => array(),
+      'url' => '',
+      'title' => 'MUST BE PROVIDED',
+      'title_arguments' => array(),
+      'title_context' => '',
+      'description' => '',
+      'parent' => 'MUST BE PROVIDED',
+      'weight' => '0',
+      'options' => array(),
+      'expanded' => '0',
+      'hidden' => '0',
+      'discovered' => '1',
+      'provider' => $this->randomName(),
+      'metadata' => array(),
+      'class' => 'Drupal\\Core\\Menu\\MenuLinkDefault',
+      'form_class' => 'Drupal\\Core\\Menu\\Form\\MenuLinkDefaultForm',
+      'id' => 'MUST BE PROVIDED',
+    );
+
+    $menu_link = MenuLinkDefault::create($container, array(), $definition['id'], $definition + $defaults);
+    $menu_link->setStringTranslation($string_translation);
+
+    return $menu_link;
+  }
+
+  /**
+   * This mocks a tree with the following structure:
+   * - 1
+   * - 2
+   *   - 3
+   *     - 4
+   * - 5
+   *   - 7
+   * - 6
+   * - 8
+   *
+   * With link 6 being the only external link.
+   */
+  protected function mockTree() {
+    $this->links = array(
+      1 => $this->mockLink(array('id' => 'test.example1', 'route_name' => 'example1', 'title' => 'foo', 'parent' => '')),
+      2 => $this->mockLink(array('id' => 'test.example2', 'route_name' => 'example2', 'title' => 'bar', 'parent' => 'test.example1', 'route_parameters' => array('foo' => 'bar'))),
+      3 => $this->mockLink(array('id' => 'test.example3', 'route_name' => 'example3', 'title' => 'baz', 'parent' => 'test.example2', 'route_parameters' => array('baz' => 'qux'))),
+      4 => $this->mockLink(array('id' => 'test.example4', 'route_name' => 'example4', 'title' => 'qux', 'parent' => 'test.example3')),
+      5 => $this->mockLink(array('id' => 'test.example5', 'route_name' => 'example5', 'title' => 'foofoo', 'parent' => '')),
+      6 => $this->mockLink(array('id' => 'test.example6', 'route_name' => '', 'url' => 'https://drupal.org/', 'title' => 'barbar', 'parent' => '')),
+      7 => $this->mockLink(array('id' => 'test.example7', 'route_name' => 'example7', 'title' => 'bazbaz', 'parent' => '')),
+      8 => $this->mockLink(array('id' => 'test.example8', 'route_name' => 'example8', 'title' => 'quxqux', 'parent' => '')),
+    );
+    $this->originalTree = array();
+    $this->originalTree[1] = array('link' => $this->links[1], 'below' => array());
+    $this->originalTree[2] = array('link' => $this->links[2], 'below' => array(
+      3 => array('link' => $this->links[3], 'below' => array(
+          4 => array('link' => $this->links[4], 'below' => array()),
+        )),
+    ));
+    $this->originalTree[5] = array('link' => $this->links[5], 'below' => array(
+      7 => array('link' => $this->links[7], 'below' => array()),
+    ));
+    $this->originalTree[6] = array('link' => $this->links[6], 'below' => array());
+    $this->originalTree[8] = array('link' => $this->links[8], 'below' => array());
+  }
+
+  /**
+   * Tests the generateIndexAndSort() tree manipulator.
+   *
+   * @covers ::generateIndexAndSort
+   */
+  public function testGenerateIndexAndSort() {
+    $this->mockTree();
+    $tree = $this->originalTree;
+    $tree = $this->defaultMenuTreeManipulators->generateIndexAndSort($tree);
+
+    // Validate that parent items #1, #2, #5 and #6 exist on the root level.
+    $this->assertEquals($this->links[1]->getPluginId(), $tree['50000 foo test.example1']['link']->getPluginId());
+    $this->assertEquals($this->links[2]->getPluginId(), $tree['50000 bar test.example2']['link']->getPluginId());
+    $this->assertEquals($this->links[5]->getPluginId(), $tree['50000 foofoo test.example5']['link']->getPluginId());
+    $this->assertEquals($this->links[6]->getPluginId(), $tree['50000 barbar test.example6']['link']->getPluginId());
+    $this->assertEquals($this->links[8]->getPluginId(), $tree['50000 quxqux test.example8']['link']->getPluginId());
+
+    // Validate that child item #4 exists at the correct location in the hierarchy.
+    $this->assertEquals($this->links[4]->getPluginId(), $tree['50000 bar test.example2']['below']['50000 baz test.example3']['below']['50000 qux test.example4']['link']->getPluginId());
+    // Validate that child item #7 exists at the correct location in the hierarchy.
+    $this->assertEquals($this->links[7]->getPluginId(), $tree['50000 foofoo test.example5']['below']['50000 bazbaz test.example7']['link']->getPluginId());
+  }
+
+  /**
+   * Tests the checkAccess() tree manipulator.
+   *
+   * @covers ::checkAccess
+   */
+  public function testCheckAccess() {
+    // Those menu links that are non-external will have their access checks
+    // performed. 8 routes, but 1 is external, 2 already have their 'access'
+    // property set, and 1 is a child if an inaccessible menu link, so only 4
+    // calls will be made.
+    $this->accessManager->expects($this->exactly(4))
+      ->method('checkNamedRoute')
+      ->will($this->returnValueMap(array(
+        array('example1', array(), $this->currentUser, NULL, FALSE),
+        array('example2', array('foo' => 'bar'), $this->currentUser, NULL, TRUE),
+        array('example3', array('baz' => 'qux'), $this->currentUser, NULL, FALSE),
+        array('example5', array(), $this->currentUser, NULL, TRUE),
+      )));
+
+    $this->mockTree();
+    $this->originalTree[5]['below'][7]['access'] = TRUE;
+    $this->originalTree[8]['access'] = FALSE;
+
+    $tree = $this->defaultMenuTreeManipulators->checkAccess($this->originalTree);
+
+    // Menu link 1: route without parameters, access forbidden, hence removed.
+    $this->assertFalse(array_key_exists(1, $tree));
+    // Menu link 2: route with parameters, access granted.
+    $item = $tree[2];
+    $this->assertTrue(array_key_exists('access', $item));
+    $this->assertTrue($item['access']);
+    // Menu link 3: route with parameters, access forbidden, hence removed,
+    // including its children.
+    $this->assertFalse(array_key_exists(3, $tree[2]['below']));
+    // Menu link 4: child of menu link 3, which already is removed.
+    $this->assertSame(array(), $tree[2]['below']);
+    // Menu link 5: no route name, treated as external, hence access granted.
+    $item = $tree[5];
+    $this->assertTrue(array_key_exists('access', $item));
+    $this->assertTrue($item['access']);
+    // Menu link 6: external URL, hence access granted.
+    $item = $tree[6];
+    $this->assertTrue(array_key_exists('access', $item));
+    $this->assertTrue($item['access']);
+    // Menu link 7: 'access' already set.
+    $item = $tree[5]['below'][7];
+    $this->assertTrue(array_key_exists('access', $item));
+    $this->assertTrue($item['access']);
+    // Menu link 8: 'access' already set, to FALSE, hence removed.
+    $this->assertFalse(array_key_exists(8, $tree));
+  }
+
+  /**
+   * Tests the flatten() tree manipulator.
+   *
+   * @covers ::flatten
+   */
+  public function testFlatten() {
+    $this->mockTree();
+    $tree = $this->defaultMenuTreeManipulators->flatten($this->originalTree);
+    $this->assertEquals(array(1, 2, 5, 6, 8), array_keys($this->originalTree));
+    $this->assertEquals(array(1, 2, 5, 6, 8, 3, 4, 7), array_keys($tree));
+  }
+
+}