diff --git a/core/core.services.yml b/core/core.services.yml
index 9f766eb..75ffe15 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -277,7 +277,7 @@ services:
     arguments: ['@plugin.manager.menu.link_tree']
   menu.tree_storage:
     class: Drupal\Core\Menu\MenuTreeStorage
-    arguments: ['@database', '@url_generator']
+    arguments: ['@database', '@url_generator', 'menu_tree']
     public: false  # This service is private to plugin.manager.menu.link_tree
   menu_link.static.overrides:
     class: Drupal\Core\Menu\StaticMenuLinkOverrides
diff --git a/core/lib/Drupal/Core/Menu/Form/MenuLinkDefaultForm.php b/core/lib/Drupal/Core/Menu/Form/MenuLinkDefaultForm.php
index 54d3098..16f0b43 100644
--- a/core/lib/Drupal/Core/Menu/Form/MenuLinkDefaultForm.php
+++ b/core/lib/Drupal/Core/Menu/Form/MenuLinkDefaultForm.php
@@ -61,9 +61,10 @@ public static function create(ContainerInterface $container) {
   }
 
   /**
-   * Injects the menu link.
+   * Injects the menu link plugin.
    *
    * @param MenuLinkInterface $menu_link
+   *   A menu link plugin instance.
    */
   public function setMenuLinkInstance(MenuLinkInterface $menu_link) {
     $this->menuLink = $menu_link;
@@ -80,7 +81,7 @@ public function buildEditForm(array &$form, array &$form_state) {
       '#title' => $this->t('This is a module-provided link. The label and path cannot be changed.'),
     );
     $form['path'] = array(
-      $this->menuLink->build(),
+      'link' => $this->menuLink->build(),
       '#type' => 'item',
       '#title' => $this->t('Link'),
     );
@@ -91,7 +92,7 @@ public function buildEditForm(array &$form, array &$form_state) {
       '#description' => $this->t('Menu links that are not enabled will not be listed in any menu.'),
       '#default_value' => !$this->menuLink->isHidden(),
     );
-     $form['expanded'] = array(
+    $form['expanded'] = array(
       '#type' => 'checkbox',
       '#title' => t('Show as expanded'),
       '#description' => $this->t('If selected and this menu link has children, the menu will always appear expanded.'),
@@ -107,7 +108,7 @@ public function buildEditForm(array &$form, array &$form_state) {
     );
 
     $options = $this->menuTree->getParentSelectOptions($this->menuLink->getPluginId());
-    $menu_parent =  $this->menuLink->getMenuName() . ':' . $this->menuLink->getParent();
+    $menu_parent = $this->menuLink->getMenuName() . ':' . $this->menuLink->getParent();
 
     if (!isset($options[$menu_parent])) {
       // Put it at the top level in the current menu.
@@ -159,4 +160,3 @@ public function submitEditForm(array &$form, array &$form_state) {
   }
 
 }
-
diff --git a/core/lib/Drupal/Core/Menu/MenuLinkTree.php b/core/lib/Drupal/Core/Menu/MenuLinkTree.php
index 4613a3a..32eb757 100644
--- a/core/lib/Drupal/Core/Menu/MenuLinkTree.php
+++ b/core/lib/Drupal/Core/Menu/MenuLinkTree.php
@@ -44,7 +44,7 @@ class MenuLinkTree implements MenuLinkTreeInterface {
     'route_name' => '',
     // Parameters for route variables when generating a link.
     'route_parameters' => array(),
-    // The external URL if this link references one (required if route_name is empty).
+    // The external URL if this link has one (required if route_name is empty).
     'url' => '',
     // The static title for the menu link.
     'title' => '',
@@ -223,7 +223,8 @@ class MenuLinkTree implements MenuLinkTreeInterface {
    * @param \Drupal\Core\Menu\StaticMenuLinkOverridesInterface $overrides
    *   Service providing overrides for static links
    * @param \Symfony\Component\HttpFoundation\RequestStack $request_stack
-   *   The request object to use for building titles and paths for plugin instances.
+   *   A request object for the controller resolver and finding the preferred
+   *   menu and link for the current page.
    * @param \Drupal\Core\Routing\RouteProviderInterface $route_provider
    *   The route provider to load routes by name.
    * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
@@ -357,6 +358,7 @@ public function hasDefinition($plugin_id) {
    * {@inheritdoc}
    *
    * @return \Drupal\Core\Menu\MenuLinkInterface
+   *   A menu link instance.
    */
   public function createInstance($plugin_id, array $configuration = array()) {
     return $this->factory->createInstance($plugin_id, $configuration);
@@ -399,7 +401,7 @@ public function loadLinks($menu_name) {
    * deleting a menu entity, so maybe we should load it and make sure it's
    * not locked?
    *
-   * @param $menu_name
+   * @param string $menu_name
    *   The name of the menu whose links will be deleted.
    */
   public function deleteLinksInMenu($menu_name) {
@@ -420,6 +422,9 @@ public function deleteLinksInMenu($menu_name) {
     Cache::invalidateTags(array('menu' => $affected_menus));
   }
 
+  /**
+   * Helper function to delete a specific instance.
+   */
   protected function deleteInstance(MenuLinkInterface $instance, $persist) {
     $id = $instance->getPluginId();
     if ($instance->isDeletable()) {
@@ -509,15 +514,12 @@ public function buildRenderTree($tree) {
       // Set a class if the link is in the active trail.
       if ($data['in_active_trail']) {
         $class[] = 'active-trail';
-        //$data['link']['localized_options']['attributes']['class'][] = 'active-trail';
       }
 
       // Allow menu-specific theme overrides.
       $element['#theme'] = 'menu_link__' . strtr($link->getMenuName(), '-', '_');
       $element['#attributes']['class'] = $class;
       $element['#title'] = $link->getTitle();
-      // @todo Use route name and parameters to generate the link path, unless
-      //    it is external.
       $element['#url'] = $link->getUrlObject();
       $element['#below'] = $data['below'] ? $this->buildRenderTree($data['below']) : array();
       $element['#original_link'] = $link;
@@ -630,7 +632,7 @@ public function getActiveMenuNames() {
   /**
    * {@inheritdoc}
    */
-  function setActiveMenuNames($menu_names = NULL) {
+  public function setActiveMenuNames(array $menu_names) {
 
     if (isset($menu_names) && is_array($menu_names)) {
       $this->activeMenus = $menu_names;
@@ -728,6 +730,7 @@ public function buildPageData($menu_name, $max_depth = NULL, $only_active_trail
    *   Is the current request happening on a 403 subrequest.
    *
    * @return array
+   *   An array of tree parameters.
    */
   protected function doBuildPageDataTreeParameters($menu_name, $max_depth, $only_active_trail, $page_is_403) {
     $tree_parameters = array(
@@ -805,7 +808,7 @@ public function buildAllData($menu_name, $id = NULL, $max_depth = NULL) {
   public function getChildLinks($id, $max_relative_depth = NULL) {
     $links = array();
     $definitions = $this->treeStorage->loadAllChildLinks($id, $max_relative_depth);
-    foreach($definitions as $id => $definition) {
+    foreach ($definitions as $id => $definition) {
       $instance = $this->menuLinkCheckAccess($definition);
       if ($instance) {
         $links[$id] = $instance;
@@ -827,7 +830,7 @@ public function getParentIds($id) {
   /**
    * {@inheritdoc}
    */
-  function getChildIds($id) {
+  public function getChildIds($id) {
     if ($this->getDefinition($id, FALSE)) {
       return $this->treeStorage->getAllChildIds($id);
     }
@@ -879,7 +882,7 @@ public function buildTree($menu_name, array $parameters = array()) {
     }
 
     if (!isset($this->menuTree[$tree_cid])) {
-      // Rebuild the links which are stored
+      // Rebuild the links which are stored.
       $data['tree'] = $this->treeStorage->loadTree($menu_name, $parameters);
       $data['route_names'] = $this->collectRoutes($data['tree']);
       // Cache the data, if it is not already in the cache.
@@ -940,6 +943,9 @@ protected function treeCheckAccess(&$tree) {
     $this->sortTree($tree);
   }
 
+  /**
+   * Helper function that recursively checks access for each item.
+   */
   protected function doTreeCheckAccess(&$tree) {
     foreach ($tree as $key => $v) {
       $definition = $tree[$key]['definition'];
@@ -991,9 +997,10 @@ protected function sortTree(&$tree) {
    *   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 $definition) {
-    // url should only be populated for external links.
+    // 'url' should only be populated for external links.
     if (!empty($definition['url']) && empty($definition['route_name'])) {
       $access = TRUE;
     }
@@ -1159,7 +1166,7 @@ public function resetLink($id) {
   /**
    * Resets the menu link to its default settings.
    *
-   * @param \Drupal\Core\Menu\MenuLinkInterface
+   * @param \Drupal\Core\Menu\MenuLinkInterface $instance
    *   The menu link which should be reset.
    *
    * @return \Drupal\Core\Menu\MenuLinkInterface
@@ -1199,6 +1206,7 @@ public function resetDefinitions() {
    * @param string $id
    *   The menu link plugin ID.
    * @param array $definition
+   *   Optional new definition for the given plugin ID.
    */
   protected function resetDefinition($id, $definition = NULL) {
     $this->definitions[$id] = $definition;
diff --git a/core/lib/Drupal/Core/Menu/MenuLinkTreeInterface.php b/core/lib/Drupal/Core/Menu/MenuLinkTreeInterface.php
index 105a869..a75e284 100644
--- a/core/lib/Drupal/Core/Menu/MenuLinkTreeInterface.php
+++ b/core/lib/Drupal/Core/Menu/MenuLinkTreeInterface.php
@@ -15,9 +15,7 @@
 interface MenuLinkTreeInterface extends PluginManagerInterface {
 
   /**
-   * Trigger discover save, and cleanup of static links
-   *
-   * @todo find a better name?
+   * Trigger discovery, save, and cleanup of static links.
    */
   public function rebuild();
 
@@ -25,6 +23,7 @@ public function rebuild();
    * The maximum depth of tree that is supported.
    *
    * @return int
+   *   The maximum depth.
    */
   public function maxDepth();
 
@@ -39,13 +38,12 @@ public function deleteLinksInMenu($menu_name);
   /**
    * Deletes a single link from the menu tree.
    *
-   * This should only be called when the link data has already been removed from
-   * any external storage.  This method will not attempt to persist the deletion
-   * except from the tree storage used by the plugin manager.
-   *
    * @param string $id
    *   The menu link plugin ID.
    * @param bool $persist
+   *   If TRUE, this method will attempt to persist the deletion from any
+   *   external storage by invoking MenuLinkInterface::deleteLink() on
+   *   the plugin that is being deleted.
    *
    * @throws \Drupal\Component\Plugin\Exception\PluginException
    *   If the $id is not valid, existing, plugin ID or if the link cannot be
@@ -105,14 +103,14 @@ public function buildRenderTree($tree);
   public function getActiveTrailIds($menu_name);
 
   /**
-   * Gets the active menu for the current page.
+   * Gets the active menus for the current page.
    *
    * The active menu for the page determines the active trail.
    *
-   * @return
+   * @return array
    *   An array of menu machine names, in order of preference. The
-   *   'system.menu:active_menus_default' config item may be used to assert a menu
-   *   order different from the order of creation, or to prevent a particular menu
+   *   'system.menu:active_menus_default' config item may be used to set a menu
+   *   order different from the default order, or to prevent a particular menu
    *   from being used at all in the active trail.
    */
   public function getActiveMenuNames();
@@ -125,8 +123,9 @@ public function getActiveMenuNames();
    * trail.
    *
    * @param array $menu_names
+   *   The menu names to use as active for the current page.
    */
-  public function setActiveMenuNames($menu_names = NULL);
+  public function setActiveMenuNames(array $menu_names);
 
   /**
    * Gets the data structure for a named menu tree, based on the current page.
@@ -200,7 +199,7 @@ public function buildAllData($menu_name, $id = NULL, $max_depth = NULL);
    *     condition key/value pairs; see _menu_build_tree() for the actual query.
    *
    * @return array
-   *   A fully built menu tree.
+   *   A fully built and access-checked menu tree.
    */
   public function buildTree($menu_name, array $parameters = array());
 
@@ -213,6 +212,7 @@ public function buildTree($menu_name, array $parameters = array());
    *   The maximum depth of child menu links relative to the passed in.
    *
    * @return array
+   *   A fully built and access-checked menu subtree.
    */
   public function buildSubtree($id, $max_relative_depth = NULL);
 
@@ -302,7 +302,8 @@ public function createLink($id, array $definition);
    *   subset of the plugin definition.
    * @param bool $persist
    *   TRUE to also have the link instance itself persist the changed values
-   *   to any additional storage.
+   *   to any additional storage by invoking MenuLinkInterface::updateLink() on
+   *   the plugin that is being updated.
    *
    * @return \Drupal\Core\Menu\MenuLinkInterface
    *   The updated menu link instance.
@@ -330,12 +331,13 @@ public function resetLink($id);
   /**
    * Gets a form instance for editing a menu link plugin.
    *
-   * @TODO Use the class resolver at some point.
+   * @todo - Use the class resolver at some point.
    *
    * @param \Drupal\Core\Menu\MenuLinkInterface $menu_link
    *   The menu link.
    *
    * @return \Drupal\Core\Menu\Form\MenuLinkFormInterface
+   *   A form instance for editing the menu link.
    */
   public function getPluginForm(MenuLinkInterface $menu_link);
 
diff --git a/core/lib/Drupal/Core/Menu/MenuTreeStorage.php b/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
index eaf2c18..3931a3a 100644
--- a/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
+++ b/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
@@ -109,7 +109,7 @@ class MenuTreeStorage implements MenuTreeStorageInterface {
    * @param array $options
    *   (optional) Any additional database connection options to use in queries.
    */
-  public function __construct(Connection $connection, UrlGeneratorInterface $url_generator,  $table = 'menu_tree', array $options = array()) {
+  public function __construct(Connection $connection, UrlGeneratorInterface $url_generator, $table, array $options = array()) {
     $this->connection = $connection;
     $this->urlGenerator = $url_generator;
     $this->table = $table;
@@ -233,7 +233,7 @@ protected function safeExecuteSelect(SelectInterface $query) {
   public function save(array $link) {
     $original = $this->loadFull($link['id']);
     // @todo - should we just return here if the links values match the original
-    //  values completely?.
+    //   values completely?.
 
     $affected_menus = array();
 
@@ -337,9 +337,9 @@ protected function preSave(array &$link, array $original) {
     // and fill parents based on the parent link.
     else {
       // @todo - we want to also check $original['has_children'] here, but that
-      //  will be 0 even if there are children if those are hidden. has_children
-      //  is really just the rendering hint. So, we either need to define
-      //  another column (has_any_children), or always do the extra query here.
+      //   will be 0 even if there are children if those are hidden.
+      //   has_children is really just the rendering hint. So, we either need
+      //   to define another column (has_any_children), or do the extra query.
       if ($original) {
         $limit = $this->maxDepth() - $this->doFindChildrenRelativeDepth($original) - 1;
       }
@@ -352,7 +352,8 @@ protected function preSave(array &$link, array $original) {
       $this->setParents($fields, $parent);
     }
 
-    // Need to check both parent and menu_name, since parent can be NULL in any menu.
+    // Need to check both parent and menu_name, since parent can be empty in any
+    // menu.
     if ($original && ($link['parent'] != $original['parent'] || $link['menu_name'] != $original['menu_name'])) {
       $this->moveChildren($fields, $original);
     }
@@ -495,11 +496,13 @@ protected function moveChildren($fields, $original) {
   /**
    * Loads the parent definition if it exists.
    *
-   * @param $link
-   * @param $original
-   * @internal param $
+   * @param array $link
+   *   The link definition to check.
+   * @param array|FALSE $original
+   *   The original link, or FALSE.
    *
-   * @return array
+   * @return array|FALSE
+   *   Returns a definition array, or FALSE if no parent was found.
    */
   protected function findParent($link, $original) {
     $parent = FALSE;
@@ -531,9 +534,10 @@ protected function findParent($link, $original) {
   }
 
   /**
-   * Sets the has_children flag for the link's parent if it has visible children.
+   * Set the has_children flag for the link's parent if it has visible children.
    *
    * @param array $link
+   *   The link to get a parent ID from.
    */
   protected function updateParentalStatus(array $link) {
     // If parent is empty, there is nothing to update.
@@ -664,7 +668,7 @@ protected function loadFullMultiple(array $ids) {
    */
   public function getRootPathIds($id) {
     $subquery = $this->connection->select($this->table, $this->options);
-    // @todo: consider making this dynamic based on static::MAX_DEPTH
+    // @todo - consider making this dynamic based on static::MAX_DEPTH
     //   or from the schema if that is generated using static::MAX_DEPTH.
     $subquery->fields($this->table, array('p1', 'p2', 'p3', 'p4', 'p5', 'p6', 'p7', 'p8', 'p9'));
     $subquery->condition('id', $id);
@@ -675,7 +679,7 @@ public function getRootPathIds($id) {
       $query->fields($this->table, array('id'));
       $query->orderBy('depth', 'DESC');
       $query->condition('mlid', $ids, 'IN');
-      // @todo: cache this result in memory if we find it's being used more
+      // @todo - cache this result in memory if we find it's being used more
       //   than once per page load.
       return $this->safeExecuteSelect($query)->fetchAllKeyed(0, 0);
     }
@@ -686,8 +690,8 @@ public function getRootPathIds($id) {
    * {@inheritdoc}
    */
   public function getExpanded($menu_name, array $parents) {
-    // @todo go back to tracking in state or some other way
-    // which menus have expanded links?
+    // @todo - go back to tracking in state or some other way
+    //   which menus have expanded links?
     do {
       $query = $this->connection->select($this->table, $this->options);
       $query->fields($this->table, array('id'));
@@ -709,7 +713,7 @@ public function getExpanded($menu_name, array $parents) {
   protected function saveRecursive($id, &$children, &$links) {
 
     if (!empty($links[$id]['parent']) && empty($links[$links[$id]['parent']])) {
-      // Invalid parent ID, so remove it
+      // Invalid parent ID, so remove it.
       $links[$id]['parent'] = '';
     }
     $this->save($links[$id]);
@@ -906,6 +910,7 @@ protected function doBuildTreeData(array $links, array $parents = array(), $dept
    *   The minimum depth to include in the returned menu tree.
    *
    * @return array
+   *   The fully build tree.
    */
   protected function treeDataRecursive(&$links, $parents, $depth) {
     $tree = array();
@@ -961,10 +966,10 @@ protected function ensureTableExists() {
         return TRUE;
       }
     }
+    catch (SchemaObjectExistsException $e) {
       // If another process has already created the config table, attempting to
       // recreate it will throw an exception. In this case just catch the
       // exception and do nothing.
-    catch (SchemaObjectExistsException $e) {
       return TRUE;
     }
     catch (\Exception $e) {
@@ -1217,7 +1222,7 @@ protected static function schemaDefinition() {
       ),
       'indexes' => array(
         'menu_parents' => array('menu_name', 'p1', 'p2', 'p3', 'p4', 'p5', 'p6', 'p7', 'p8', 'p9'),
-        // @todo test this index for effectiveness.
+        // @todo - test this index for effectiveness.
         'menu_parent_expand_child' => array('menu_name', 'expanded', 'has_children', array('parent', 16)),
         'route_values' => array(array('route_name', 32), array('route_param_key', 16)),
       ),
diff --git a/core/lib/Drupal/Core/Menu/MenuTreeStorageInterface.php b/core/lib/Drupal/Core/Menu/MenuTreeStorageInterface.php
index 3f1d80b..d90a767 100644
--- a/core/lib/Drupal/Core/Menu/MenuTreeStorageInterface.php
+++ b/core/lib/Drupal/Core/Menu/MenuTreeStorageInterface.php
@@ -13,6 +13,7 @@
    * The maximum depth of tree the storage implementation supports.
    *
    * @return int
+   *   The maximum depth.
    */
   public function maxDepth();
 
@@ -31,6 +32,7 @@ public function rebuild(array $definitions);
    *
    * @param string $id
    *   The menu link plugin ID.
+   *
    * @return array|FALSE
    *   Menu Link definition
    */
@@ -40,7 +42,7 @@ public function load($id);
    * Loads multiple plugin definitions from the storage.
    *
    * @param array $ids
-   *  An array of plugin IDs.
+   *   An array of plugin IDs.
    *
    * @return array
    *   An array of menu Link definitions.
@@ -70,7 +72,7 @@ public function loadByProperties(array $properties);
    *   Defaults to FALSE.
    *
    * @return array
-   *  An array of menu link definitions keyed by ID.
+   *   An array of menu link definitions keyed by ID.
    */
   public function loadByRoute($route_name, array $route_parameters = array(), $include_hidden = FALSE);
 
@@ -176,6 +178,7 @@ public function getAllChildIds($id);
    *   The maximum depth of child menu links relative to the passed in.
    *
    * @return array
+   *   A fully built menu subtree.
    */
   public function loadSubtree($id, $max_relative_depth = NULL);
 
@@ -194,12 +197,15 @@ public function loadSubtree($id, $max_relative_depth = NULL);
   public function getRootPathIds($id);
 
   /**
+   * Find expanded links in a menu given a set of possible parents.
+   *
    * @param string $menu_name
    *   The menu name.
    * @param array $parents
+   *   One or more parent IDs to match.
    *
    * @return array
-   *   The menu link ID that are flagged as expanded in this menu.
+   *   The menu link IDs that are flagged as expanded in this menu.
    */
   public function getExpanded($menu_name, array $parents);
 
diff --git a/core/lib/Drupal/Core/Menu/StaticMenuLinkOverrides.php b/core/lib/Drupal/Core/Menu/StaticMenuLinkOverrides.php
index 50d2d2c..0c7a94b 100644
--- a/core/lib/Drupal/Core/Menu/StaticMenuLinkOverrides.php
+++ b/core/lib/Drupal/Core/Menu/StaticMenuLinkOverrides.php
@@ -35,6 +35,12 @@ class StaticMenuLinkOverrides implements StaticMenuLinkOverridesInterface {
    */
   protected $configFactory;
 
+  /**
+   * Constructs a StaticMenuLinkOverrides object.
+   *
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   A configuration factory instance.
+   */
   public function __construct(ConfigFactoryInterface $config_factory) {
     $this->configFactory = $config_factory;
   }
@@ -118,7 +124,14 @@ public function loadMultipleOverrides(array $ids) {
    */
   public function saveOverride($id, array $definition) {
     // Remove unexpected keys.
-    $definition = array_intersect_key($definition, array('menu_name' => 1, 'parent' => 1, 'weight' => 1, 'expanded' => 1, 'hidden' => 1));
+    $expected = array(
+      'menu_name' => 1,
+      'parent' => 1,
+      'weight' => 1,
+      'expanded' => 1,
+      'hidden' => 1,
+    );
+    $definition = array_intersect_key($definition, $expected);
     if ($definition) {
       $id = static::encodeId($id);
       $all_overrides = $this->getConfig()->get('definitions');
@@ -137,6 +150,7 @@ public function saveOverride($id, array $definition) {
    *
    * @param string $id
    *   The menu plugin ID.
+   *
    * @return string
    *   The menu plugin ID with double underscore instead of dots.
    */
diff --git a/core/modules/menu_link_content/menu_link_content.install b/core/modules/menu_link_content/menu_link_content.install
index 03fe225..606ca6a 100644
--- a/core/modules/menu_link_content/menu_link_content.install
+++ b/core/modules/menu_link_content/menu_link_content.install
@@ -17,4 +17,3 @@ function menu_link_content_uninstall() {
     $menu_tree->deleteLink("menu_link_content:$uuid", FALSE);
   }
 }
-
diff --git a/core/modules/menu_link_content/menu_link_content.module b/core/modules/menu_link_content/menu_link_content.module
index 5e6ff93..6648280 100644
--- a/core/modules/menu_link_content/menu_link_content.module
+++ b/core/modules/menu_link_content/menu_link_content.module
@@ -1,9 +1,14 @@
 <?php
 
+/**
+ * @file
+ * Enables users to create menu link content.
+ */
+
 use Drupal\system\MenuInterface;
 
 /**
- * Implements hook_menu_delete()
+ * Implements hook_menu_delete().
  */
 function menu_link_content_menu_delete(MenuInterface $menu) {
   $storage = \Drupal::entityManager()->getStorage('menu_link_content');
diff --git a/core/modules/menu_link_content/src/Controller/MenuController.php b/core/modules/menu_link_content/src/Controller/MenuController.php
index 5f93db8..7ffa9f8 100644
--- a/core/modules/menu_link_content/src/Controller/MenuController.php
+++ b/core/modules/menu_link_content/src/Controller/MenuController.php
@@ -32,4 +32,3 @@ public function addLink(MenuInterface $menu) {
   }
 
 }
-
diff --git a/core/modules/menu_link_content/src/Entity/MenuLinkContent.php b/core/modules/menu_link_content/src/Entity/MenuLinkContent.php
index 347d577..c98ef42 100644
--- a/core/modules/menu_link_content/src/Entity/MenuLinkContent.php
+++ b/core/modules/menu_link_content/src/Entity/MenuLinkContent.php
@@ -181,9 +181,10 @@ public function getWeight() {
   }
 
   /**
-   * Builds up the menu plugin definition for this entity.
+   * Builds up the menu link plugin definition for this entity.
    *
    * @return array
+   *   The plugin definition corresponding to this entity.
    *
    * @see \Drupal\Core\Menu\MenuLinkTree::$defaults
    */
@@ -308,8 +309,8 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
 
     $fields['menu_name'] = FieldDefinition::create('string')
       ->setLabel(t('Menu name'))
-      ->setDescription(t('The menu name. All links with the same menu name (such as "tools") are part of the same menu.'));
-      //      ->setSetting('default_value', 'tools')
+      ->setDescription(t('The menu name. All links with the same menu name (such as "tools") are part of the same menu.'))
+      ->setSetting('default_value', 'tools');
 
     // @todo use a link field in the end? see https://drupal.org/node/2235457
     $fields['route_name'] = FieldDefinition::create('string')
@@ -379,4 +380,3 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
   }
 
 }
-
diff --git a/core/modules/menu_link_content/src/Entity/MenuLinkContentInterface.php b/core/modules/menu_link_content/src/Entity/MenuLinkContentInterface.php
index acf1a4c..35a24a7 100644
--- a/core/modules/menu_link_content/src/Entity/MenuLinkContentInterface.php
+++ b/core/modules/menu_link_content/src/Entity/MenuLinkContentInterface.php
@@ -22,7 +22,8 @@ public function setInsidePlugin();
   /**
    * Gets the title of the menu link.
    *
-   * @return mixed
+   * @return string
+   *   The title of the link.
    */
   public function getTitle();
 
@@ -38,6 +39,7 @@ public function getRouteName();
    * Gets the route parameters of the custom menu link.
    *
    * @return array
+   *   The route parameters, or an empty array.
    */
   public function getRouteParameters();
 
@@ -64,6 +66,7 @@ public function getUrl();
    * Gets the url object pointing to the URL of the custom menu link.
    *
    * @return \Drupal\Core\Url
+   *   A Url object instance.
    */
   public function getUrlObject();
 
@@ -76,9 +79,10 @@ public function getUrlObject();
   public function getMenuName();
 
   /**
-   * Gets the query options of the custom menu link.
+   * Gets the options for the custom menu link.
    *
    * @return array
+   *   The options that may be passed to the URL generator.
    */
   public function getOptions();
 
@@ -96,6 +100,7 @@ public function setOptions(array $options);
    * Gets the description of the custom menu link for the UI.
    *
    * @return string
+   *   The descption for use on admin pages or as a title attribute.
    */
   public function getDescription();
 
@@ -103,6 +108,7 @@ public function getDescription();
    * Gets the menu plugin ID associated with this entity.
    *
    * @return string
+   *   The plugin ID.
    */
   public function getPluginId();
 
@@ -118,13 +124,15 @@ public function isHidden();
    * Returns whether the menu link is marked as always expanded.
    *
    * @return bool
+   *   TRUE for expanded, FALSE otherwise.
    */
   public function isExpanded();
 
   /**
-   * Gets the menu plugin ID of the parent menu link.
+   * Gets the plugin ID of the parent menu link.
    *
    * @return string
+   *   A plugin ID, or empty string if this link is at the top level.
    */
   public function getParentId();
 
@@ -132,6 +140,7 @@ public function getParentId();
    * Returns the weight of the custom menu link.
    *
    * @return int
+   *   A weight for use when ordering links.
    */
   public function getWeight();
 
diff --git a/core/modules/menu_link_content/src/Form/MenuLinkContentForm.php b/core/modules/menu_link_content/src/Form/MenuLinkContentForm.php
index 6ad7c8a..272ac64 100644
--- a/core/modules/menu_link_content/src/Form/MenuLinkContentForm.php
+++ b/core/modules/menu_link_content/src/Form/MenuLinkContentForm.php
@@ -147,6 +147,7 @@ public function submitEditForm(array &$form, array &$form_state) {
    * Break up a user-entered URL or path into all the relevant parts.
    *
    * @param string $url
+   *   The user-entered URL or path.
    *
    * @return array
    *   The extracted parts.
@@ -176,7 +177,7 @@ protected function extractUrl($url) {
       }
       catch (ParamNotConvertedException $e) {
         // A path like node/99 matched a route, but the route parameter was
-        // invalid (e.g. node with ID 99 does not exist)
+        // invalid (e.g. node with ID 99 does not exist).
       }
     }
     return $extracted;
@@ -256,7 +257,7 @@ public function form(array $form, array &$form_state) {
     if ($url->isExternal()) {
       $default_value = $url->toString();
     }
-    elseif($url->getRouteName() == '<front>') {
+    elseif ($url->getRouteName() == '<front>') {
       // The default route for new entities is <front>, but we just want an
       // empty form field.
       $default_value = $this->getEntity()->isNew() ? '' : '<front>';
@@ -283,7 +284,7 @@ public function form(array $form, array &$form_state) {
     );
 
     $options = $this->menuTree->getParentSelectOptions($this->entity->getPluginId());
-    $menu_parent =  $this->entity->getMenuName() . ':' . $this->entity->getParentId();
+    $menu_parent = $this->entity->getMenuName() . ':' . $this->entity->getParentId();
 
     if (!isset($options[$menu_parent])) {
       // Put it at the top level in the current menu.
@@ -312,6 +313,9 @@ protected function actions(array $form, array &$form_state) {
     return $element;
   }
 
+  /**
+   * {@inheritdoc}
+   */
   public function validate(array $form, array &$form_state) {
     $this->doValidate($form, $form_state);
 
@@ -387,7 +391,7 @@ protected function doValidate(array $form, array &$form_state) {
       if ($extracted['path'] != $normal_path) {
         drupal_set_message($this->t('The menu system stores system paths only, but will use the URL alias for display. %link_path has been stored as %normal_path', array(
           '%link_path' => $extracted['path'],
-          '%normal_path' => $normal_path
+          '%normal_path' => $normal_path,
         )));
       }
     }
diff --git a/core/modules/menu_link_content/src/MenuLinkContentAccessController.php b/core/modules/menu_link_content/src/MenuLinkContentAccessController.php
index fd59e28..d895478 100644
--- a/core/modules/menu_link_content/src/MenuLinkContentAccessController.php
+++ b/core/modules/menu_link_content/src/MenuLinkContentAccessController.php
@@ -30,16 +30,13 @@ protected function checkAccess(EntityInterface $entity, $operation, $langcode, A
       case 'view':
         // There is no direct view.
         return FALSE;
-        break;
 
       case 'update':
         // If there is a URL, this is an external link so always accessible.
         return $account->hasPermission('administer menu') && ($entity->getUrl() || $this->accessManager()->checkNamedRoute($entity->getRouteName(), $entity->getRouteParameters(), $account));
-        break;
 
       case 'delete':
         return !$entity->isNew() && $account->hasPermission('administer menu');
-        break;
     }
   }
 
@@ -55,4 +52,4 @@ protected function accessManager() {
     }
     return $this->accessManager;
   }
-}
\ No newline at end of file
+}
diff --git a/core/modules/menu_link_content/src/Plugin/Menu/MenuLinkContent.php b/core/modules/menu_link_content/src/Plugin/Menu/MenuLinkContent.php
index 8ef24fb..15c5370 100644
--- a/core/modules/menu_link_content/src/Plugin/Menu/MenuLinkContent.php
+++ b/core/modules/menu_link_content/src/Plugin/Menu/MenuLinkContent.php
@@ -104,6 +104,7 @@ public static function create(ContainerInterface $container, array $configuratio
    * Loads the entity associated with this menu link.
    *
    * @return \Drupal\menu_link_content\Entity\MenuLinkContentInterface
+   *   The menu link content entity.
    *
    * @throws \Drupal\Component\Plugin\Exception\PluginException
    *   If the entity ID and uuid are both invalid or missing.
@@ -184,11 +185,11 @@ public function getEditRoute() {
    */
   public function getTranslateRoute() {
     $entity_type = $this->getEntity()->getEntityType()->id();
-    return array (
+    return array(
       'route_name' => 'content_translation.translation_overview_' . $entity_type,
-      'route_parameters' => array (
-         $entity_type => $this->getEntity()->id(),
-       )
+      'route_parameters' => array(
+        $entity_type => $this->getEntity()->id(),
+      ),
     );
   }
 
diff --git a/core/modules/menu_link_content/src/Tests/MenuLinkContentUITest.php b/core/modules/menu_link_content/src/Tests/MenuLinkContentUITest.php
index c3952f2..7bbcf80 100644
--- a/core/modules/menu_link_content/src/Tests/MenuLinkContentUITest.php
+++ b/core/modules/menu_link_content/src/Tests/MenuLinkContentUITest.php
@@ -35,7 +35,7 @@ public static function getInfo() {
   /**
    * {@inheritdoc}
    */
-  function setUp() {
+  protected function setUp() {
     $this->entityTypeId = 'menu_link_content';
     $this->bundle = 'menu_link_content';
     $this->fieldName = 'title';
@@ -61,4 +61,3 @@ protected function createEntity($values, $langcode, $bundle_name = NULL) {
   }
 
 }
-
diff --git a/core/modules/menu_ui/menu_ui.admin.inc b/core/modules/menu_ui/menu_ui.admin.inc
index 2021be0..00d3e58 100644
--- a/core/modules/menu_ui/menu_ui.admin.inc
+++ b/core/modules/menu_ui/menu_ui.admin.inc
@@ -11,10 +11,13 @@
 /**
  * Returns HTML for the menu overview form into a table.
  *
- * @param $variables
+ * @param array $variables
  *   An associative array containing:
  *   - form: A render element representing the form.
  *
+ * @return string
+ *   The themed HTML.
+ *
  * @ingroup themeable
  */
 function theme_menu_overview_form($variables) {
@@ -37,7 +40,8 @@ function theme_menu_overview_form($variables) {
       $element['id']['#attributes']['class'] = array('menu-id');
       $element['weight']['#attributes']['class'] = array('menu-weight');
 
-      // Change the parent field to a hidden. This allows any value but hides the field.
+      // Change the parent field to a hidden. This allows any value but hides
+      // the field.
       $element['parent']['#type'] = 'hidden';
 
       $indent = array(
diff --git a/core/modules/menu_ui/src/Form/MenuLinkResetForm.php b/core/modules/menu_ui/src/Form/MenuLinkResetForm.php
index 7d1ef62..2fb02d7 100644
--- a/core/modules/menu_ui/src/Form/MenuLinkResetForm.php
+++ b/core/modules/menu_ui/src/Form/MenuLinkResetForm.php
@@ -52,6 +52,9 @@ public static function create(ContainerInterface $container) {
     );
   }
 
+  /**
+   * {@inheritdoc}
+   */
   public function getFormId() {
     return 'menu_link_reset_confirm';
   }
diff --git a/core/modules/menu_ui/src/MenuForm.php b/core/modules/menu_ui/src/MenuForm.php
index d182789..c1eba69 100644
--- a/core/modules/menu_ui/src/MenuForm.php
+++ b/core/modules/menu_ui/src/MenuForm.php
@@ -112,7 +112,7 @@ public function form(array $form, array &$form_state) {
     // Add menu links administration form for existing menus.
     if (!$menu->isNew() || $menu->isLocked()) {
       // Form API supports constructing and validating self-contained sections
-      // within forms, but does not allow to handle the form section's submission
+      // within forms, but does not allow handling the form section's submission
       // equally separated yet. Therefore, we use a $form_state key to point to
       // the parents of the form section.
       // @see self::submitOverviewForm()
@@ -167,6 +167,9 @@ public function save(array $form, array &$form_state) {
     $form_state['redirect_route'] = $this->entity->urlInfo('edit-form');
   }
 
+  /**
+   * Recursively count the number of menu links in a tree.
+   */
   protected function countElements($tree, $count = 0) {
     foreach ($tree as $element) {
       $count++;
@@ -296,9 +299,9 @@ protected function buildOverviewTreeForm($tree, $delta) {
           $operations['delete']['title'] = $this->t('Delete');
         }
         if ($item->isTranslatable()) {
-          $operations['translate'] = array (
+          $operations['translate'] = array(
             'title' => $this->t('Translate'),
-          ) + (array)$item->getTranslateRoute();
+          ) + (array) $item->getTranslateRoute();
         }
         $form[$id]['operations'] = array(
           '#type' => 'operations',
@@ -317,7 +320,7 @@ protected function buildOverviewTreeForm($tree, $delta) {
    * Submit handler for the menu overview form.
    *
    * This function takes great care in saving parent items first, then items
-   * underneath them. Saving items in the incorrect order can break the menu tree.
+   * underneath them. Saving items in the incorrect order can break the tree.
    */
   protected function submitOverviewForm(array $complete_form, array &$form_state) {
     // Form API supports constructing and validating self-contained sections
diff --git a/core/modules/menu_ui/src/Plugin/Menu/LocalAction/MenuLinkAdd.php b/core/modules/menu_ui/src/Plugin/Menu/LocalAction/MenuLinkAdd.php
index ad27fce..88e1898 100644
--- a/core/modules/menu_ui/src/Plugin/Menu/LocalAction/MenuLinkAdd.php
+++ b/core/modules/menu_ui/src/Plugin/Menu/LocalAction/MenuLinkAdd.php
@@ -30,4 +30,3 @@ public function getOptions(Request $request) {
   }
 
 }
-
diff --git a/core/modules/menu_ui/src/Tests/MenuCacheTagsTest.php b/core/modules/menu_ui/src/Tests/MenuCacheTagsTest.php
index c7402bc..138c132 100644
--- a/core/modules/menu_ui/src/Tests/MenuCacheTagsTest.php
+++ b/core/modules/menu_ui/src/Tests/MenuCacheTagsTest.php
@@ -67,7 +67,6 @@ public function testMenuBlock() {
     );
     $this->verifyPageCache($path, 'HIT', $expected_tags);
 
-
     // Verify that after modifying the menu, there is a cache miss.
     $this->pass('Test modification of menu.', 'Debug');
     $menu->label = 'Awesome llama';
@@ -77,7 +76,6 @@ public function testMenuBlock() {
     // Verify a cache hit.
     $this->verifyPageCache($path, 'HIT');
 
-
     // Verify that after modifying the menu link weight, there is a cache miss.
     $menu_tree->updateLink('test_page_test.test_page', array('weight' => -10));
     $this->pass('Test modification of menu link.', 'Debug');
@@ -86,7 +84,6 @@ public function testMenuBlock() {
     // Verify a cache hit.
     $this->verifyPageCache($path, 'HIT');
 
-
     // Verify that after adding a menu link, there is a cache miss.
 
     $this->pass('Test addition of menu link.', 'Debug');
@@ -104,7 +101,6 @@ public function testMenuBlock() {
     // Verify a cache hit.
     $this->verifyPageCache($path, 'HIT');
 
-
     // Verify that after resetting the first menu link, there is a cache miss.
     $this->pass('Test reset of menu link.', 'Debug');
     $this->assertTrue($menu_link->isResetable(), 'First link can be reset');