diff --git a/core/modules/system/lib/Drupal/system/Controller/ThemeController.php b/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
index 61461b8..e0b119c 100644
--- a/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
+++ b/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
@@ -9,12 +9,15 @@
 
 use Drupal\Core\Config\Config;
 use Drupal\Core\Controller\ControllerBase;
+use Drupal\Core\Controller\ControllerInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
 
 /**
  * Controller for theme handling.
  */
-class ThemeController implements ControllerInterface {
+class ThemeController extends ControllerBase implements ControllerInterface {
 
   /**
    * The system.theme config object.
@@ -52,6 +55,9 @@ public static function create(ContainerInterface $container) {
   /**
    * Disables a theme.
    *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   A request object containing a theme name and a valid token.
+   *
    * @return \Symfony\Component\HttpFoundation\RedirectResponse
    *   Redirects back to the appearance admin page.
    *
@@ -59,9 +65,9 @@ public static function create(ContainerInterface $container) {
    *   Throws access denied when no theme or token is set in the request or when
    *   the token is invalid.
    */
-  public function disable() {
-    $theme = $this->request->get('theme');
-    $token = $this->request->get('token');
+  public function disable(Request $request) {
+    $theme = $request->get('theme');
+    $token = $request->get('token');
 
     if (isset($theme) && isset($token) && drupal_valid_token($token, 'system-theme-operation-link')) {
       // Get current list of themes.
@@ -91,6 +97,9 @@ public function disable() {
   /**
    * Enables a theme.
    *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   A request object containing a theme name and a valid token.
+   *
    * @return \Symfony\Component\HttpFoundation\RedirectResponse
    *   Redirects back to the appearance admin page.
    *
@@ -98,9 +107,9 @@ public function disable() {
    *   Throws access denied when no theme or token is set in the request or when
    *   the token is invalid.
    */
-  public function enable() {
-    $theme = $this->request->get('theme');
-    $token = $this->request->get('token');
+  public function enable(Request $request) {
+    $theme = $request->get('theme');
+    $token = $request->get('token');
 
     if (isset($theme) && isset($token) && drupal_valid_token($token, 'system-theme-operation-link')) {
       // Get current list of themes.
@@ -122,7 +131,10 @@ public function enable() {
   }
 
   /**
-   * Set the default theme.
+   * Sets the default theme.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   A request object containing a theme name and a valid token.
    *
    * @return \Symfony\Component\HttpFoundation\RedirectResponse
    *   Redirects back to the appearance admin page.
@@ -131,12 +143,12 @@ public function enable() {
    *   Throws access denied when no theme or token is set in the request or when
    *   the token is invalid.
    */
-  public function defaultTheme() {
+  public function defaultTheme(Request $request) {
     // Set the page title.
     drupal_set_title($this->t('Set default theme'));
 
-    $theme = $this->request->query->get('theme');
-    $token = $this->request->query->get('token');
+    $theme = $request->query->get('theme');
+    $token = $request->query->get('token');
     if (isset($theme) && isset($token) && drupal_valid_token($token, 'system-theme-operation-link')) {
       // Get current list of themes.
       $themes = list_themes();
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index df7ef6f..e3acffb 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -198,57 +198,6 @@ function system_themes_admin_form_submit($form, &$form_state) {
 }
 
 /**
- * Menu callback; Set the default theme.
- */
-function system_theme_default() {
-  $request = Drupal::request();
-  $theme = $request->get('theme');
-  $token = $request->get('token');
-  if (!empty($theme) && !empty($token) && drupal_valid_token($token, 'system-theme-operation-link')) {
-    // 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.
-      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.
-      $admin_theme = Drupal::config('system.theme')->get('admin');
-      if ($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