diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index b6f7fed..8eeb57f 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -137,17 +137,17 @@ function block_menu() {
   //   hook_menu_local_tasks() to check for the untranslated tab_parent path.
   // @see http://drupal.org/node/1067408
   foreach (list_themes() as $key => $theme) {
-    $items['admin/structure/block/list/' . $key] = array(
+    $items["admin/structure/block/list/$key"] = array(
       'title' => check_plain($theme->info['name']),
       'type' => $key == $default_theme ? MENU_DEFAULT_LOCAL_TASK : MENU_LOCAL_TASK,
-      'route_name' => 'block_admin_display.' . $key,
+      'route_name' => "block_admin_display.$key",
     );
-    $items['admin/structure/block/list/' . $key . '/add'] = array(
+    $items["admin/structure/block/list/$key/add"] = array(
       'title' => 'Place blocks',
       'type' => MENU_LOCAL_ACTION,
-      'route_name' => 'block_plugin_ui.' . $key,
+      'route_name' => "block_plugin_ui.$key",
     );
-    $items['admin/structure/block/demo/' . $key] = array(
+    $items["admin/structure/block/demo/$key"] = array(
       'title' => check_plain($theme->info['name']),
       'page callback' => 'block_admin_demo',
       'page arguments' => array($key),
diff --git a/core/modules/block/lib/Drupal/block/Controller/BlockAutocompleteController.php b/core/modules/block/lib/Drupal/block/Controller/BlockAutocompleteController.php
index 7eb6dda..539a8c1 100644
--- a/core/modules/block/lib/Drupal/block/Controller/BlockAutocompleteController.php
+++ b/core/modules/block/lib/Drupal/block/Controller/BlockAutocompleteController.php
@@ -28,7 +28,7 @@ class BlockAutocompleteController implements ControllerInterface {
   protected $manager;
 
   /**
-   * Constructs a new PlaceBlocksForm object.
+   * Constructs a new BlockAutocompleteController object.
    *
    * @param \Drupal\Component\Plugin\PluginManagerInterface $manager
    *   The block plugin manager.
diff --git a/core/modules/block/lib/Drupal/block/Controller/BlockListController.php b/core/modules/block/lib/Drupal/block/Controller/BlockListController.php
index c1fa2b5..b699903 100644
--- a/core/modules/block/lib/Drupal/block/Controller/BlockListController.php
+++ b/core/modules/block/lib/Drupal/block/Controller/BlockListController.php
@@ -64,8 +64,8 @@ public static function create(ContainerInterface $container) {
    *   A render array as expected by drupal_render().
    */
   public function listing($theme = NULL) {
-    $default_theme = $theme ?: $this->configFactory->get('system.theme')->get('default');
-    return $this->blockListController->render($default_theme);
+    $theme = $theme ?: $this->configFactory->get('system.theme')->get('default');
+    return $this->blockListController->render($theme);
   }
 
 }
diff --git a/core/modules/block/lib/Drupal/block/Form/PlaceBlocksForm.php b/core/modules/block/lib/Drupal/block/Form/PlaceBlocksForm.php
index ad661ac..ffc4b9e 100644
--- a/core/modules/block/lib/Drupal/block/Form/PlaceBlocksForm.php
+++ b/core/modules/block/lib/Drupal/block/Form/PlaceBlocksForm.php
@@ -8,6 +8,7 @@
 namespace Drupal\block\Form;
 
 use Drupal\Component\Plugin\PluginManagerInterface;
+use Drupal\Component\Utility\String;
 use Drupal\Core\Controller\ControllerInterface;
 use Drupal\Core\Form\FormInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -25,6 +26,8 @@ class PlaceBlocksForm implements FormInterface, ControllerInterface {
   protected $manager;
 
   /**
+   * The theme this block will be placed into.
+   *
    * @var string
    */
   protected $theme;
@@ -63,13 +66,13 @@ public function buildForm(array $form, array &$form_state, $theme = NULL, $categ
     $form['#theme'] = 'system_plugin_ui_form';
     $rows = array();
     $categories = array();
-    foreach ($this->manager->getDefinitions() as $plugin_id => $display_plugin_definition) {
-      if (empty($category) || $display_plugin_definition['category'] == $category) {
-        $rows[$plugin_id] = $this->row($plugin_id, $display_plugin_definition);
+    foreach ($this->manager->getDefinitions() as $plugin_id => $plugin_definition) {
+      if (empty($category) || $plugin_definition['category'] == $category) {
+        $rows[$plugin_id] = $this->row($plugin_id, $plugin_definition);
       }
-      $categories[$display_plugin_definition['category']] = array(
-        'title' => $display_plugin_definition['category'],
-        'href' => 'admin/structure/block/list/' . $this->theme . '/add/' . $display_plugin_definition['category'],
+      $categories[$plugin_definition['category']] = array(
+        'title' => $plugin_definition['category'],
+        'href' => 'admin/structure/block/list/' . $this->theme . '/add/' . $plugin_definition['category'],
       );
     }
 
@@ -112,23 +115,23 @@ public function buildForm(array $form, array &$form_state, $theme = NULL, $categ
   /**
    * Generates the row data for a single block plugin.
    *
-   * @param string $display_plugin_id
+   * @param string $plugin_id
    *   The plugin ID.
-   * @param array $display_plugin_definition
+   * @param array $plugin_definition
    *   The plugin definition.
    *
    * @return array
    *   The row data for a single block plugin.
    */
-  public function row($display_plugin_id, array $display_plugin_definition) {
+  protected function row($plugin_id, array $plugin_definition) {
     $row = array();
-    $row[] = check_plain($display_plugin_definition['admin_label']);
+    $row[] = String::checkPlain($plugin_definition['admin_label']);
     $row[] = array('data' => array(
       '#type' => 'operations',
       '#links' => array(
         'configure' => array(
           'title' => t('Place block'),
-          'href' => 'admin/structure/block/add/' . $display_plugin_id . '/' . $this->theme,
+          'href' => 'admin/structure/block/add/' . $plugin_id . '/' . $this->theme,
         ),
       ),
     ));
diff --git a/core/modules/block/lib/Drupal/block/Routing/RouteSubscriber.php b/core/modules/block/lib/Drupal/block/Routing/RouteSubscriber.php
index 2cc0c5e..de32cd1 100644
--- a/core/modules/block/lib/Drupal/block/Routing/RouteSubscriber.php
+++ b/core/modules/block/lib/Drupal/block/Routing/RouteSubscriber.php
@@ -39,22 +39,28 @@ public function routes(RouteBuildEvent $event) {
     $collection = $event->getRouteCollection();
     foreach (list_themes(TRUE) as $key => $theme) {
       // The block entity listing page.
-      $route = new Route('admin/structure/block/list/' . $key, array(
-        '_controller' => '\Drupal\block\Controller\BlockListController::listing',
-        'theme' => $key,
-      ), array(
-        '_block_themes_access' => 'TRUE',
-      ));
+      $route = new Route(
+        "admin/structure/block/list/$key",
+        array(
+          '_controller' => '\Drupal\block\Controller\BlockListController::listing',
+          'theme' => $key,
+        ),
+        array(
+          '_block_themes_access' => 'TRUE',
+        )
+      );
       $collection->add("block_admin_display.$key", $route);
 
       // The block plugin listing page.
-      $route = new Route('admin/structure/block/list/' . $key . '/add/{category}', array(
-        '_form' => '\Drupal\block\Form\PlaceBlocksForm',
-        'category' => NULL,
-        'theme' => $key,
-      ), array(
-        '_block_themes_access' => 'TRUE',
-      ));
+      $route = new Route(
+        "admin/structure/block/list/$key/add/{category}",
+        array(
+          '_form' => '\Drupal\block\Form\PlaceBlocksForm',
+          'category' => NULL,
+          'theme' => $key,
+        ),
+        array('_block_themes_access' => 'TRUE')
+      );
       $collection->add("block_plugin_ui.$key", $route);
     }
   }