diff --git a/core/modules/system/lib/Drupal/system/Controller/SystemController.php b/core/modules/system/lib/Drupal/system/Controller/SystemController.php
index fce6ba1..34a387e 100644
--- a/core/modules/system/lib/Drupal/system/Controller/SystemController.php
+++ b/core/modules/system/lib/Drupal/system/Controller/SystemController.php
@@ -321,12 +321,4 @@ public function themesPage() {
     return $build;
   }
 
-  /**
-   * @todo Remove system_theme_default().
-   */
-  public function themeSetDefault() {
-    module_load_include('admin.inc', 'system');
-    return system_theme_default();
-  }
-
 }
diff --git a/core/modules/system/lib/Drupal/system/Controller/ThemeController.php b/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
index 852d2b6..c397612 100644
--- a/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
+++ b/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
@@ -7,60 +7,60 @@
 
 namespace Drupal\system\Controller;
 
-use Drupal\Core\Config\Config;
+use Drupal\Core\Controller\ControllerBase;
 use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Drupal\Core\Extension\ThemeHandlerInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
-use Symfony\Component\HttpFoundation\RedirectResponse;
+use Drupal\Core\Access\CsrfTokenGenerator;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+use Symfony\Component\HttpFoundation\RedirectResponse;
 
 /**
  * Controller for theme handling.
  */
-class ThemeController implements ContainerInjectionInterface {
-
-  /**
-   * The system.theme config object.
-   *
-   * @var \Drupal\Core\Config\Config
-   */
-  protected $config;
+class ThemeController extends ControllerBase implements ContainerInjectionInterface {
 
   /**
-   * Constructs a ThemeController object.
-   *
-   * @param \Drupal\Core\Config\Config $config
-   *   The config.
+   * @var \Drupal\Core\Extension\ThemeHandlerInterface
+   *   The theme handler.
    */
-  public function __construct(Config $config) {
-    $this->config = $config;
-  }
+  protected $themeHandler;
 
   /**
    * {@inheritdoc}
    */
   public static function create(ContainerInterface $container) {
     return new static(
-      $container->get('config.factory')->get('system.theme')
+      $container->get('theme_handler')
     );
   }
 
   /**
+   * Constructs a Theme Controller Object.
+   *
+   * @param \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler
+   *   The theme handler.
+   */
+  public function __construct(ThemeHandlerInterface $theme_handler) {
+    $this->themeHandler = $theme_handler;
+  }
+
+  /**
    * Disables a theme.
    *
    * @param \Symfony\Component\HttpFoundation\Request $request
-   *   A request object containing a theme name and a valid token.
+   *   A request object containing a theme name.
    *
    * @return \Symfony\Component\HttpFoundation\RedirectResponse
    *   Redirects back to the appearance admin page.
    *
    * @throws \Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException
-   *   Throws access denied when no theme or token is set in the request or when
-   *   the token is invalid.
+   *   Throws access denied when no theme set in the request
    */
   public function disable(Request $request) {
     $theme = $request->get('theme');
-
+    $config = $this->config('system.theme');
     if (isset($theme)) {
       // Get current list of themes.
       $themes = list_themes();
@@ -68,19 +68,16 @@ public function disable(Request $request) {
       // Check if the specified theme is one recognized by the system.
       if (!empty($themes[$theme])) {
         // Do not disable the default or admin theme.
-        if ($theme === $this->config->get('default') || $theme === $this->config->get('admin')) {
-          drupal_set_message(t('%theme is the default theme and cannot be disabled.', array('%theme' => $themes[$theme]->info['name'])), 'error');
+        if ($theme === $config->get('default') || $theme === $config->get('admin')) {
+          drupal_set_message($this->t('%theme is the default theme and cannot be disabled.', array('%theme' => $themes[$theme]->info['name'])), 'error');
         }
         else {
-          theme_disable(array($theme));
-          drupal_set_message(t('The %theme theme has been disabled.', array('%theme' => $themes[$theme]->info['name'])));
+          $this->themeHandler->disable(array($theme));
+          drupal_set_message($this->t('The %theme theme has been disabled.', array('%theme' => $themes[$theme]->info['name'])));
         }
       }
-      else {
-        drupal_set_message(t('The %theme theme was not found.', array('%theme' => $theme)), 'error');
-      }
 
-      return new RedirectResponse(url('admin/appearance', array('absolute' => TRUE)));
+      return $this->redirect('system.themes_page');
     }
 
     throw new AccessDeniedHttpException();
@@ -90,14 +87,13 @@ public function disable(Request $request) {
    * Enables a theme.
    *
    * @param \Symfony\Component\HttpFoundation\Request $request
-   *   A request object containing a theme name and a valid token.
+   *   A request object containing a theme name.
    *
    * @return \Symfony\Component\HttpFoundation\RedirectResponse
    *   Redirects back to the appearance admin page.
    *
    * @throws \Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException
-   *   Throws access denied when no theme or token is set in the request or when
-   *   the token is invalid.
+   *   Throws access denied when no theme is set in the request.
    */
   public function enable(Request $request) {
     $theme = $request->get('theme');
@@ -108,17 +104,80 @@ public function enable(Request $request) {
 
       // Check if the specified theme is one recognized by the system.
       if (!empty($themes[$theme])) {
-        theme_enable(array($theme));
-        drupal_set_message(t('The %theme theme has been enabled.', array('%theme' => $themes[$theme]->info['name'])));
+        $this->themeHandler->enable(array($theme));
+        drupal_set_message($this->t('The %theme theme has been enabled.', array('%theme' => $themes[$theme]->info['name'])));
       }
       else {
-        drupal_set_message(t('The %theme theme was not found.', array('%theme' => $theme)), 'error');
+        drupal_set_message($this->t('The %theme theme was not found.', array('%theme' => $theme)), 'error');
       }
 
-      return new RedirectResponse(url('admin/appearance', array('absolute' => TRUE)));
+      return $this->redirect('system.themes_page');
+
     }
 
     throw new AccessDeniedHttpException();
   }
 
+  /**
+   * Set the default theme.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   A request object containing a theme name.
+   *
+   * @return \Symfony\Component\HttpFoundation\RedirectResponse
+   *   Redirects back to the appearance admin page.
+   *
+   * @throws \Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException
+   *   Throws access denied when no theme is set in the request.
+   */
+  public function defaultTheme(Request $request) {
+    $config = $this->config('system.theme');
+    $theme = $request->query->get('theme');
+
+    if (isset($theme)) {
+      // Get current list of themes.
+      $themes = list_themes();
+
+      // Check if the specified theme is one recognized by the system.
+      if (!empty($themes[$theme])) {
+        // Enable the theme if it is currently disabled.
+        if (empty($themes[$theme]->status)) {
+          $this->themeHandler->enable(array($theme));
+        }
+
+        // Set the default theme.
+        $config->set('default', $theme)->save();
+
+        // Rebuild the menu. This duplicates the menu_router_rebuild() in
+        // theme_enable(). However, modules must know the current default theme
+        // in order to use this information in hook_menu() or hook_menu_alter()
+        // implementations, and doing the variable_set() before the
+        // theme_enable() could result in a race condition where the theme is
+        // default but not enabled.
+        menu_router_rebuild();
+
+        // The status message depends on whether an admin theme is currently in
+        // use: a value of 0 means the admin theme is set to be the default
+        // theme.
+        $admin_theme = $config->get('admin');
+        if ($admin_theme != 0 && $admin_theme != $theme) {
+          drupal_set_message($this->t('Please note that the administration theme is still set to the %admin_theme theme; consequently, the theme on this page remains unchanged. All non-administrative sections of the site, however, will show the selected %selected_theme theme by default.', array(
+            '%admin_theme' => $themes[$admin_theme]->info['name'],
+            '%selected_theme' => $themes[$theme]->info['name'],
+          )));
+        }
+        else {
+          drupal_set_message($this->t('%theme is now the default theme.', array('%theme' => $themes[$theme]->info['name'])));
+        }
+      }
+      else {
+        drupal_set_message($this->t('The %theme theme was not found.', array('%theme' => $theme)), 'error');
+      }
+
+      return $this->redirect('system.themes_page');
+
+    }
+    throw new AccessDeniedHttpException();
+  }
+
 }
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index 697f8c7..1f91617 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -9,58 +9,6 @@
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
 
 /**
- * Menu callback; Set the default theme.
- */
-function system_theme_default() {
-  $request = \Drupal::request();
-  $theme = $request->get('theme');
-  if (!empty($theme)) {
-    // Get current list of themes.
-    $themes = list_themes();
-
-    // Check if the specified theme is one recognized by the system.
-    if (!empty($themes[$theme])) {
-      // Enable the theme if it is currently disabled.
-      if (empty($themes[$theme]->status)) {
-       theme_enable(array($theme));
-      }
-      // Set the default theme.
-      \Drupal::config('system.theme')
-        ->set('default', $theme)
-        ->save();
-
-      // Rebuild the menu. This duplicates the menu_router_rebuild() in
-      // theme_enable(). However, modules must know the current default theme in
-      // order to use this information in hook_menu() or hook_menu_alter()
-      // implementations, and doing the variable_set() before the theme_enable()
-      // could result in a race condition where the theme is default but not
-      // enabled.
-      \Drupal::service('router.builder')->rebuild();
-      menu_router_rebuild();
-      \Drupal::cache('cache')->deleteTags(array('local_task' => 1));
-
-      // The status message depends on whether an admin theme is currently in use:
-      // a value of 0 means the admin theme is set to be the default theme.
-      $admin_theme = \Drupal::config('system.theme')->get('admin');
-      if ($admin_theme != 0 && $admin_theme != $theme) {
-        drupal_set_message(t('Please note that the administration theme is still set to the %admin_theme theme; consequently, the theme on this page remains unchanged. All non-administrative sections of the site, however, will show the selected %selected_theme theme by default.', array(
-          '%admin_theme' => $themes[$admin_theme]->info['name'],
-          '%selected_theme' => $themes[$theme]->info['name'],
-        )));
-      }
-      else {
-        drupal_set_message(t('%theme is now the default theme.', array('%theme' => $themes[$theme]->info['name'])));
-      }
-    }
-    else {
-      drupal_set_message(t('The %theme theme was not found.', array('%theme' => $theme)), 'error');
-    }
-    return new RedirectResponse(url('admin/appearance', array('absolute' => TRUE)));
-  }
-  throw new AccessDeniedHttpException();
-}
-
-/**
  * Recursively check compatibility.
  *
  * @param $incompatible
@@ -218,6 +166,7 @@ function theme_admin_page($variables) {
 function theme_system_admin_index($variables) {
   $menu_items = $variables['menu_items'];
 
+  $stripe = 0;
   $container = array('left' => '', 'right' => '');
   $flip = array('left' => 'right', 'right' => 'left');
   $position = 'left';
@@ -422,12 +371,7 @@ function theme_system_modules_details($variables) {
     $rows[] = $row;
   }
 
-  $table = array(
-    '#theme' => 'table',
-    '#header' => $form['#header'],
-    '#rows' => $rows,
-  );
-  return drupal_render($table);
+  return theme('table', array('header' => $form['#header'], 'rows' => $rows));
 }
 
 /**
diff --git a/core/modules/system/system.routing.yml b/core/modules/system/system.routing.yml
index 4d27aa6..a353b77 100644
--- a/core/modules/system/system.routing.yml
+++ b/core/modules/system/system.routing.yml
@@ -319,7 +319,7 @@ system.theme_set_default:
   path: '/admin/appearance/default'
   defaults:
     _title: 'Set default theme'
-    _content: '\Drupal\system\Controller\SystemController::themeSetDefault'
+    _content: '\Drupal\system\Controller\ThemeController::defaultTheme'
   requirements:
     _permission: 'administer themes'
     _csrf_token: 'TRUE'