diff --git a/core/lib/Drupal/Core/Theme/Registry.php b/core/lib/Drupal/Core/Theme/Registry.php
index 861a010..3893338 100644
--- a/core/lib/Drupal/Core/Theme/Registry.php
+++ b/core/lib/Drupal/Core/Theme/Registry.php
@@ -146,7 +146,7 @@ protected function init($theme_name = NULL) {
     if (!isset($theme_name)) {
       // #1: The theme registry might get instantiated before the theme was
       // initialized. Cope with that.
-      if (!isset($GLOBALS['theme_info'])) {
+      if (!isset($GLOBALS['theme_info']) || !isset($GLOBALS['theme'])) {
         unset($this->runtimeRegistry);
         unset($this->registry);
         drupal_theme_initialize();
@@ -307,9 +307,9 @@ public function getBaseHook($hook) {
   protected function build($theme, array $base_theme, $theme_engine) {
     $cache = array();
     // First, preprocess the theme hooks advertised by modules. This will
-    // serve as the basic registry. Since the list of enabled modules is the same
-    // regardless of the theme used, this is cached in its own entry to save
-    // building it for every theme.
+    // serve as the basic registry. Since the list of enabled modules is the
+    // same regardless of the theme used, this is cached in its own entry to
+    // save building it for every theme.
     if ($cached = $this->cache->get('theme_registry:build:modules')) {
       $cache = $cached->data;
     }
@@ -361,19 +361,19 @@ protected function build($theme, array $base_theme, $theme_engine) {
    *
    * @param $cache
    *   The theme registry that will eventually be cached; It is an associative
-   *   array keyed by theme hooks, whose values are associative arrays describing
-   *   the hook:
+   *   array keyed by theme hooks, whose values are associative arrays
+   *   describing the hook:
    *   - 'type': The passed-in $type.
    *   - 'theme path': The passed-in $path.
    *   - 'function': The name of the function generating output for this theme
    *     hook. Either defined explicitly in hook_theme() or, if neither
    *     'function' nor 'template' is defined, then the default theme function
-   *     name is used. The default theme function name is the theme hook prefixed
-   *     by either 'theme_' for modules or '$name_' for everything else. If
-   *     'function' is defined, 'template' is not used.
+   *     name is used. The default theme function name is the theme hook
+   *     prefixed by either 'theme_' for modules or '$name_' for everything
+   *     else. If 'function' is defined, 'template' is not used.
    *   - 'template': The filename of the template generating output for this
-   *     theme hook. The template is in the directory defined by the 'path' key of
-   *     hook_theme() or defaults to "$path/templates".
+   *     theme hook. The template is in the directory defined by the 'path' key
+   *     of hook_theme() or defaults to "$path/templates".
    *   - 'variables': The variables for this theme hook as defined in
    *     hook_theme(). If there is more than one implementation and 'variables'
    *     is not specified in a later one, then the previous definition is kept.
@@ -382,19 +382,19 @@ protected function build($theme, array $base_theme, $theme_engine) {
    *     'render element' is not specified in a later one, then the previous
    *     definition is kept.
    *   - 'preprocess functions': See theme() for detailed documentation.
-   * @param $name
+   * @param string $name
    *   The name of the module, theme engine, base theme engine, theme or base
    *   theme implementing hook_theme().
-   * @param $type
+   * @param string $type
    *   One of 'module', 'theme_engine', 'base_theme_engine', 'theme', or
-   *   'base_theme'. Unlike regular hooks that can only be implemented by modules,
-   *   each of these can implement hook_theme(). _theme_process_registry() is
-   *   called in aforementioned order and new entries override older ones. For
-   *   example, if a theme hook is both defined by a module and a theme, then the
-   *   definition in the theme will be used.
-   * @param $theme
+   *   'base_theme'. Unlike regular hooks that can only be implemented by
+   *   modules, each of these can implement hook_theme().
+   *   _theme_process_registry() is called in aforementioned order and new
+   *   entries override older ones. For example, if a theme hook is both defined
+   *   by a module and a theme, then the definition in the theme will be used.
+   * @param \stdClass $theme
    *   The loaded $theme object as returned from list_themes().
-   * @param $path
+   * @param string $path
    *   The directory where $name is. For example, modules/system or
    *   themes/bartik.
    *
@@ -572,7 +572,8 @@ public function destruct() {
   }
 
   /**
-   * @param $module
+   * Wraps drupal_get_path().
+   *
    * @return string
    */
   protected function getPath($module) {
@@ -580,14 +581,19 @@ protected function getPath($module) {
   }
 
   /**
+   * Wraps list_themes().
+   *
    * @return array
    */
   protected function listThemes() {
     return list_themes();
   }
 
+  /**
+   * Wraps drupal_theme_initialize().
+   */
   protected function initializeTheme() {
     return drupal_theme_initialize();
   }
 
-} 
+}
diff --git a/core/lib/Drupal/Core/Utility/ThemeRegistry.php b/core/lib/Drupal/Core/Utility/ThemeRegistry.php
index 7ef77cc..e09ed65 100644
--- a/core/lib/Drupal/Core/Utility/ThemeRegistry.php
+++ b/core/lib/Drupal/Core/Utility/ThemeRegistry.php
@@ -50,7 +50,7 @@ class ThemeRegistry extends CacheCollector implements DestructableInterface {
    * @param bool $modules_loaded
    *   Whether all modules have already been loaded.
    */
-  function __construct($cid, CacheBackendInterface $cache, LockBackendInterface $lock, $tags, $modules_loaded = FALSE) {
+  function __construct($cid, CacheBackendInterface $cache, LockBackendInterface $lock, $tags = array(), $modules_loaded = FALSE) {
     $this->cid = $cid;
     $this->cache = $cache;
     $this->lock = $lock;
@@ -74,6 +74,9 @@ function __construct($cid, CacheBackendInterface $cache, LockBackendInterface $l
       foreach (array_keys($this->storage) as $key) {
         $this->persist($key);
       }
+      // RegistryTest::testRaceCondition() ensures that the cache entry is
+      // written on the initial construction of the theme registry.
+      $this->updateCache();
     }
   }
 
diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/RegistryTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/RegistryTest.php
index 5ab43ca..3e4d6af 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Theme/RegistryTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/RegistryTest.php
@@ -35,17 +35,19 @@ public static function getInfo() {
    * Tests the behavior of the theme registry class.
    */
   function testRaceCondition() {
-    $_SERVER['REQUEST_METHOD'] = 'GET';
+    \Drupal::request()->setMethod('GET');
     $cid = 'test_theme_registry';
 
     // Directly instantiate the theme registry, this will cause a base cache
     // entry to be written in __construct().
-    $registry = new ThemeRegistry($cid, 'cache', array('theme_registry' => TRUE), $this->container->get('module_handler')->isLoaded());
+    $cache = \Drupal::cache('cache');
+    $lock_backend = \Drupal::lock();
+    $registry = new ThemeRegistry($cid, $cache, $lock_backend, array('theme_registry' => TRUE), $this->container->get('module_handler')->isLoaded());
 
     $this->assertTrue(cache()->get($cid), 'Cache entry was created.');
 
     // Trigger a cache miss for an offset.
-    $this->assertTrue($registry['theme_test_template_test'], 'Offset was returned correctly from the theme registry.');
+    $this->assertTrue($registry->get('theme_test_template_test'), 'Offset was returned correctly from the theme registry.');
     // This will cause the ThemeRegistry class to write an updated version of
     // the cache entry when it is destroyed, usually at the end of the request.
     // Before that happens, manually delete the cache entry we created earlier
@@ -53,15 +55,15 @@ function testRaceCondition() {
     cache()->delete($cid);
 
     // Destroy the class so that it triggers a cache write for the offset.
-    unset($registry);
+    $registry->destruct();
 
     $this->assertTrue(cache()->get($cid), 'Cache entry was created.');
 
     // Create a new instance of the class. Confirm that both the offset
     // requested previously, and one that has not yet been requested are both
     // available.
-    $registry = new ThemeRegistry($cid, 'cache', array('theme_registry' => TRUE));
-    $this->assertTrue($registry['theme_test_template_test'], 'Offset was returned correctly from the theme registry');
-    $this->assertTrue($registry['theme_test_template_test_2'], 'Offset was returned correctly from the theme registry');
+    $registry = new ThemeRegistry($cid, $cache, $lock_backend, array('theme_registry' => TRUE), $this->container->get('module_handler')->isLoaded());
+    $this->assertTrue($registry->get('theme_test_template_test'), 'Offset was returned correctly from the theme registry');
+    $this->assertTrue($registry->get('theme_test_template_test_2'), 'Offset was returned correctly from the theme registry');
   }
 }
diff --git a/core/modules/system/tests/modules/theme_test/lib/Drupal/theme_test/EventSubscriber/ThemeTestSubscriber.php b/core/modules/system/tests/modules/theme_test/lib/Drupal/theme_test/EventSubscriber/ThemeTestSubscriber.php
index 56cbdaf..41129cc 100644
--- a/core/modules/system/tests/modules/theme_test/lib/Drupal/theme_test/EventSubscriber/ThemeTestSubscriber.php
+++ b/core/modules/system/tests/modules/theme_test/lib/Drupal/theme_test/EventSubscriber/ThemeTestSubscriber.php
@@ -7,6 +7,9 @@
 
 namespace Drupal\theme_test\EventSubscriber;
 
+use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Symfony\Component\DependencyInjection\ContainerAware;
+use Symfony\Component\DependencyInjection\IntrospectableContainerInterface;
 use Symfony\Component\HttpKernel\KernelEvents;
 use Symfony\Component\HttpKernel\Event\GetResponseEvent;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
@@ -14,7 +17,14 @@
 /**
  * Theme test subscriber for controller requests.
  */
-class ThemeTestSubscriber implements EventSubscriberInterface {
+class ThemeTestSubscriber extends ContainerAware implements EventSubscriberInterface {
+
+  /**
+   * The used container.
+   *
+   * @var \Symfony\Component\DependencyInjection\IntrospectableContainerInterface
+   */
+  protected $container;
 
   /**
    * Generates themed output early in a page request.
@@ -36,10 +46,18 @@ public function onRequest(GetResponseEvent $event) {
       // returning output and theming the page as a whole.
       $GLOBALS['theme_test_output'] = theme('more_link', array('url' => 'user', 'title' => 'Themed output generated in a KernelEvents::REQUEST listener'));
     }
+  }
+
+  /**
+   * Ensures that the theme registry was not initialized.
+   */
+  public function onView(GetResponseEvent $event) {
+    $request = $event->getRequest();
+    $current_path = $request->attributes->get('_system_path');
     if (strpos($current_path, 'user/autocomplete') === 0) {
-      // Register a fake registry loading callback. If it gets called by
-      // theme_get_registry(), the registry has not been initialized yet.
-      _theme_registry_callback('_theme_test_load_registry', array());
+      if ($this->container->initialized('theme.registry')) {
+        throw new \Exception('registry initialized');
+      }
     }
   }
 
@@ -48,6 +66,7 @@ public function onRequest(GetResponseEvent $event) {
    */
   static function getSubscribedEvents() {
     $events[KernelEvents::REQUEST][] = array('onRequest');
+    $events[KernelEvents::VIEW][] = array('onView', -1000);
     return $events;
   }
 
diff --git a/core/modules/system/tests/modules/theme_test/theme_test.module b/core/modules/system/tests/modules/theme_test/theme_test.module
index b48e712..87e26b8 100644
--- a/core/modules/system/tests/modules/theme_test/theme_test.module
+++ b/core/modules/system/tests/modules/theme_test/theme_test.module
@@ -79,13 +79,6 @@ function theme_test_menu() {
   );
   return $items;
 }
-/**
- * Fake registry loading callback.
- */
-function _theme_test_load_registry() {
-  print 'registry initialized';
-  return array();
-}
 
 /**
  * Custom theme callback.
diff --git a/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php b/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php
index 099f614..8445150 100644
--- a/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php
+++ b/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php
@@ -72,6 +72,7 @@ public function testGetRegistryForModule() {
     ));
     $this->registry->setBaseThemes(array());
 
+    // Include the module so that hook_theme can be called.
     include_once DRUPAL_ROOT . '/core/modules/system/tests/modules/theme_test/theme_test.module';
     $this->moduleHandler->expects($this->once())
       ->method('getImplementations')