diff --git a/core/includes/module.inc b/core/includes/module.inc
index 00a0da2..557f6dc 100644
--- a/core/includes/module.inc
+++ b/core/includes/module.inc
@@ -9,26 +9,18 @@
 use Drupal\Core\Extension\ExtensionDiscovery;
 
 /**
- * Builds a list of bootstrap modules and enabled modules and themes.
+ * Builds a list of enabled themes.
  *
  * @param $type
  *   The type of list to return:
- *   - module: All enabled modules.
- *   - bootstrap: All enabled modules required for bootstrap.
- *   - theme: All themes.
+ *   - theme: All enabled themes.
  *
  * @return
- *   An associative array of modules or themes, keyed by name. For $type
- *   'bootstrap' and 'module_enabled', the array values equal the keys.
+ *   An associative array of themes, keyed by name.
  *   For $type 'theme', the array values are objects representing the
  *   respective database row, with the 'info' property already unserialized.
  *
  * @see list_themes()
- *
- * @todo There are too many layers/levels of caching involved for system_list()
- *   data. Consider to add a \Drupal::config($name, $cache = TRUE) argument to allow
- *   callers like system_list() to force-disable a possible configuration
- *   storage controller cache or some other way to circumvent it/take it over.
  */
 function system_list($type) {
   $lists = &drupal_static(__FUNCTION__);
@@ -42,21 +34,12 @@ function system_list($type) {
     );
     // Build a list of themes.
     $enabled_themes = (array) \Drupal::config('system.theme')->get('enabled');
-    array_walk($enabled_themes, function (&$value, $key) {
-      $value = 'system.theme.data.' . $key;
-    });
-    $theme_data = (array) \Drupal::state()->getMultiple($enabled_themes);
-    // @todo Remove me?
-    if (0 && empty($theme_data)) {
-      // system_list() may be called from _drupal_bootstrap_code() and
-      // which case system.module is not loaded yet.
-      // Prevent a filesystem scan in drupal_load() and include it directly.
-      require_once DRUPAL_ROOT . '/core/modules/system/system.module';
-      $theme_data = system_rebuild_theme_data();
-    }
+
+    $theme_data = \Drupal::state()->get('system.theme.data', array());
+
     foreach ($theme_data as $name => $theme) {
+      $theme->status = (int) isset($enabled_themes[$name]);
       $lists['theme'][$name] = $theme;
-      // Build a list of filenames so drupal_get_filename can use it.
       $lists['filepaths'][] = array(
         'type' => 'theme',
         'name' => $name,
@@ -80,7 +63,6 @@ function system_list($type) {
 function system_list_reset() {
   drupal_static_reset('system_list');
   drupal_static_reset('system_rebuild_module_data');
-  drupal_static_reset('system_rebuild_theme_data');
   drupal_static_reset('list_themes');
   \Drupal::cache('bootstrap')->delete('system_list');
   \Drupal::cache()->delete('system_info');
@@ -91,13 +73,6 @@ function system_list_reset() {
   // \Drupal\Core\Extension\ModuleHandler::alter() and the fact that profiles
   // are recorded and handled as modules.
   Cache::invalidateTags(array('extension' => TRUE));
-
-  // Rebuild theme data to update theme states.
-  // When enabling a module that implements hook_system_info_alter() to inject a
-  // new (testing) theme or manipulate an existing theme, then that will cause
-  // system_list_reset() to be called, but theme data is not necessarily rebuilt
-  // afterwards.
-  system_rebuild_theme_data();
 }
 
 /**
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index f98df80..ba0412d 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -974,7 +974,7 @@ function theme_settings_convert_to_config(array $theme_settings, Config $config)
  * @see \Drupal\Core\Extension\ThemeHandler::enable().
  */
 function theme_enable($theme_list) {
-  \Drupal::service('theme_handler')->enable($theme_list);
+  return \Drupal::service('theme_handler')->enable($theme_list);
 }
 
 /**
@@ -989,7 +989,7 @@ function theme_enable($theme_list) {
  * @see \Drupal\Core\Extension\ThemeHandler::disable().
  */
 function theme_disable($theme_list) {
-  \Drupal::service('theme_handler')->disable($theme_list);
+  return \Drupal::service('theme_handler')->disable($theme_list);
 }
 
 /**
diff --git a/core/includes/theme.maintenance.inc b/core/includes/theme.maintenance.inc
index 3d4d8a9..9c87bd2 100644
--- a/core/includes/theme.maintenance.inc
+++ b/core/includes/theme.maintenance.inc
@@ -20,6 +20,11 @@
 function _drupal_maintenance_theme() {
   global $theme, $theme_key;
 
+  // If $theme is already set, assume the others are set too, and do nothing.
+  if (isset($theme)) {
+    return;
+  }
+
   require_once DRUPAL_ROOT . '/' . Settings::get('path_inc', 'core/includes/path.inc');
   require_once __DIR__ . '/theme.inc';
   require_once __DIR__ . '/common.inc';
@@ -67,7 +72,7 @@ function _drupal_maintenance_theme() {
   }
 
   // Ensure that system.module is loaded.
-  if (!function_exists('_system_rebuild_theme_data')) {
+  if (!function_exists('system_rebuild_theme_data')) {
     $module_handler = \Drupal::moduleHandler();
     $module_handler->addModule('system', 'core/modules/system');
     $module_handler->load('system');
@@ -79,7 +84,9 @@ function _drupal_maintenance_theme() {
   // If retrieval failed or no themes are installed yet, or if the requested
   // custom theme is not installed, retrieve all available themes.
   if (empty($themes) || !isset($themes[$custom_theme])) {
-    $themes = _system_rebuild_theme_data();
+    $theme_handler = \Drupal::service('theme_handler');
+    $themes = $theme_handler->rebuildThemeData();
+    $theme_handler->addTheme($themes[$custom_theme]);
   }
 
   // list_themes() triggers a \Drupal\Core\Extension\ModuleHandler::alter() in
diff --git a/core/lib/Drupal/Core/Extension/ThemeHandler.php b/core/lib/Drupal/Core/Extension/ThemeHandler.php
index 9c437de..78c7a2b 100644
--- a/core/lib/Drupal/Core/Extension/ThemeHandler.php
+++ b/core/lib/Drupal/Core/Extension/ThemeHandler.php
@@ -41,7 +41,7 @@ class ThemeHandler implements ThemeHandlerInterface {
    *
    * @var array
    */
-  protected $list = array();
+  protected $list;
 
   /**
    * The config factory to get the enabled themes.
@@ -128,48 +128,53 @@ public function __construct(ConfigFactoryInterface $config_factory, ModuleHandle
    * @todo Rename to install().
    */
   public function enable(array $theme_list, $enable_dependencies = TRUE) {
+    $theme_config = $this->configFactory->get('system.theme');
+    $disabled_themes = $this->configFactory->get('system.theme.disabled');
     if ($enable_dependencies) {
       // Get all theme data so we can find dependencies and sort.
-      $theme_data = $this->rebuildThemeData();
-      // Create an associative array with weights as values.
-      $theme_list = array_flip(array_values($theme_list));
+      $theme_data = system_rebuild_theme_data();
+      $theme_list = array_combine($theme_list, $theme_list);
 
-      while (list($theme) = each($theme_list)) {
-        if (!isset($theme_data[$theme])) {
-          // This theme is not found in the filesystem, abort.
-          return FALSE;
-        }
-        if ($theme_data[$theme]->status) {
-          // Skip already enabled themes.
-          unset($theme_list[$theme]);
-          continue;
-        }
-        $theme_list[$theme] = $theme_data[$theme]->sort;
+      if (array_diff_key($theme_list, $theme_data)) {
+        // One or more of the given themes doesn't exist.
+        return FALSE;
+      }
+
+      // Only process themes that are not enabled currently.
+      $installed_themes = $theme_config->get('enabled') ?: array();
+      if (!$theme_list = array_diff_key($theme_list, $installed_themes)) {
+        // Nothing to do. All themes already enabled.
+        return TRUE;
+      }
+      $installed_themes += $disabled_themes->get() ?: array();
 
-        // Add dependencies to the list, with a placeholder weight.
-        // The new themes will be processed as the while loop continues.
+      while (list($theme) = each($theme_list)) {
+        // Add dependencies to the list. The new themes will be processed as
+        // the while loop continues.
         foreach (array_keys($theme_data[$theme]->requires) as $dependency) {
-          if (!isset($theme_list[$dependency])) {
-            $theme_list[$dependency] = 0;
+          if (!isset($theme_data[$dependency])) {
+            // The dependency does not exist.
+            return FALSE;
           }
-        }
 
-        if (!$theme_list) {
-          // Nothing to do. All themes already enabled.
-          return TRUE;
+          // Skip already installed themes.
+          if (!isset($theme_list[$dependency]) && !isset($installed_themes[$dependency])) {
+            $theme_list[$dependency] = $dependency;
+          }
         }
       }
 
-      // Sort the theme list by pre-calculated weights.
+      // Set the actual theme weights.
+      $theme_list = array_map(function ($theme) use ($theme_data) {
+        return $theme_data[$theme]->sort;
+      }, $theme_list);
+
+      // Sort the theme list by their weights (reverse).
       arsort($theme_list);
       $theme_list = array_keys($theme_list);
     }
 
-    $this->clearCssCache();
     $themes_installed = array();
-    $themes_enabled = array();
-    $theme_config = $this->configFactory->get('system.theme');
-    $disabled_themes = $this->configFactory->get('system.theme.disabled');
     foreach ($theme_list as $key) {
       // Only process themes that are not already enabled.
       $enabled = $theme_config->get("enabled.$key") !== NULL;
@@ -196,14 +201,19 @@ public function enable(array $theme_list, $enable_dependencies = TRUE) {
       // Install default configuration of the theme.
       $this->configInstaller->installDefaultConfig('theme', $key);
 
+      $themes_installed[] = $key;
+
       // Record the fact that it was installed.
       watchdog('system', '%theme theme installed.', array('%theme' => $key), WATCHDOG_INFO);
     }
 
     $this->resetSystem();
+    $this->clearCssCache();
 
     // Invoke hook_themes_enabled() after the themes have been enabled.
-    $this->moduleHandler->invokeAll('themes_enabled', array($theme_list));
+    $this->moduleHandler->invokeAll('themes_enabled', array($themes_installed));
+
+    return !empty($themes_installed);
   }
 
   /**
@@ -214,10 +224,7 @@ public function enable(array $theme_list, $enable_dependencies = TRUE) {
   public function disable(array $theme_list) {
     // Don't disable the default theme.
     if ($pos = array_search($this->configFactory->get('system.theme')->get('default'), $theme_list) !== FALSE) {
-      unset($theme_list[$pos]);
-      if (empty($theme_list)) {
-        return;
-      }
+      throw new \RuntimeException('The current default theme cannot be disabled.');
     }
 
     $this->clearCssCache();
@@ -243,52 +250,41 @@ public function disable(array $theme_list) {
    * {@inheritdoc}
    */
   public function listInfo() {
-    if (empty($this->list)) {
+    if (!isset($this->list)) {
       $this->list = array();
-      try {
-        $themes = $this->systemThemeList();
-      }
-      catch (\Exception $e) {
-        // If the database is not available, rebuild the theme data.
-        $themes = $this->rebuildThemeData();
-      }
-
+      $themes = $this->systemThemeList();
       foreach ($themes as $theme) {
-        foreach ($theme->info['stylesheets'] as $media => $stylesheets) {
-          foreach ($stylesheets as $stylesheet => $path) {
-            $theme->stylesheets[$media][$stylesheet] = $path;
-          }
-        }
-        foreach ($theme->info['scripts'] as $script => $path) {
-          $theme->scripts[$script] = $path;
-        }
-        if (isset($theme->info['engine'])) {
-          $theme->engine = $theme->info['engine'];
-        }
-        if (isset($theme->info['base theme'])) {
-          $theme->base_theme = $theme->info['base theme'];
-        }
-        // Status is normally retrieved from the database. Add zero values when
-        // read from the installation directory to prevent notices.
-        if (!isset($theme->status)) {
-          $theme->status = 0;
-        }
-        $this->list[$theme->getName()] = $theme;
+        $this->addTheme($theme);
       }
     }
     return $this->list;
   }
 
+  public function addTheme(Extension $theme) {
+    // @todo Remove this 100% unnecessary duplication of properties.
+    foreach ($theme->info['stylesheets'] as $media => $stylesheets) {
+      foreach ($stylesheets as $stylesheet => $path) {
+        $theme->stylesheets[$media][$stylesheet] = $path;
+      }
+    }
+    foreach ($theme->info['scripts'] as $script => $path) {
+      $theme->scripts[$script] = $path;
+    }
+    if (isset($theme->info['engine'])) {
+      $theme->engine = $theme->info['engine'];
+    }
+    if (isset($theme->info['base theme'])) {
+      $theme->base_theme = $theme->info['base theme'];
+    }
+    $this->list[$theme->getName()] = $theme;
+  }
+
   /**
    * {@inheritdoc}
    */
   public function reset() {
-    // listInfo() calls system_info() which has a lot of side effects that have
-    // to be triggered like the classloading of theme classes.
-    $this->list = array();
+    $this->list = NULL;
     $this->systemListReset();
-    $this->listInfo();
-    $this->list = array();
   }
 
   /**
@@ -338,8 +334,7 @@ public function rebuildThemeData() {
 
       if (!empty($theme->info['base theme'])) {
         $sub_themes[] = $key;
-        // Add the defined base theme as dependency to the theme, in order to
-        // re-use the dependency graph resolution of _module_build_dependencies().
+        // Add the base theme as a proper dependency.
         $themes[$key]->info['dependencies'][] = $themes[$key]->info['base theme'];
       }
 
diff --git a/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php b/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php
index 013f8b9..92ab92f 100644
--- a/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php
+++ b/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php
@@ -18,19 +18,12 @@
    * @param array $theme_list
    *   An array of theme names.
    * @param bool $enable_dependencies
-   *   If TRUE, dependencies will automatically be added and enabled in the
+   *   (optional) If TRUE, dependencies will automatically be installed in the
    *   correct order. This incurs a significant performance cost, so use FALSE
    *   if you know $theme_list is already complete and in the correct order.
    *
    * @throws \Drupal\Core\Extension\ExtensionNameLengthException
    *   Thrown when the theme name is to long
-   *
-   * @todo D8: This is almost identical to module_enable() now. Only differences:
-   *   - There is no required default .theme PHP file to load.
-   *   - There is no schema to install.
-   *   - System list, state, theme list, and static resets slightly differ.
-   * @todo hook_themes_installed(), hook_themes_enabled(), etc are not invoked in
-   *   themes, since they are excluded from the hook system.
    */
   public function enable(array $theme_list, $enable_dependencies = TRUE);
 
@@ -43,13 +36,10 @@ public function enable(array $theme_list, $enable_dependencies = TRUE);
   public function disable(array $theme_list);
 
   /**
-   * Returns a list of all currently available themes.
-   *
-   * Retrieved from the database, if available and the site is not in
-   * maintenance mode; otherwise compiled freshly from the filesystem.
+   * Returns a list of currently enabled themes.
    *
    * @return \Drupal\Core\Extension\Extension[]
-   *   An associative array of the currently available themes. The keys are the
+   *   An associative array of the currently enabled themes. The keys are the
    *   themes' machine names and the values are objects having the following
    *   properties:
    *   - filename: The filepath and name of the .info.yml file.
diff --git a/core/lib/Drupal/Core/Installer/InstallerServiceProvider.php b/core/lib/Drupal/Core/Installer/InstallerServiceProvider.php
index 2389a62..6c393b1 100644
--- a/core/lib/Drupal/Core/Installer/InstallerServiceProvider.php
+++ b/core/lib/Drupal/Core/Installer/InstallerServiceProvider.php
@@ -30,11 +30,10 @@ public function register(ContainerBuilder $container) {
     $container->register('config.storage', 'Drupal\Core\Config\InstallStorage');
 
     // Replace services with in-memory implementations.
-    foreach (array('bootstrap', 'config', 'cache', 'menu', 'page', 'path') as $bin) {
-      $container
-        ->register("cache.$bin", 'Drupal\Core\Cache\MemoryBackend')
-        ->addArgument($bin);
-    }
+    $definition = $container->getDefinition('cache_factory');
+    $definition->setClass('Drupal\Core\Cache\MemoryBackendFactory');
+    $definition->setArguments(array());
+    $definition->setMethodCalls(array());
     $container
       ->register('keyvalue', 'Drupal\Core\KeyValueStore\KeyValueMemoryFactory');
     $container
diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockAdminThemeTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockAdminThemeTest.php
index 181f5b9..d553440 100644
--- a/core/modules/block/lib/Drupal/block/Tests/BlockAdminThemeTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockAdminThemeTest.php
@@ -37,9 +37,9 @@ function testAdminTheme() {
     $admin_user = $this->drupalCreateUser(array('administer blocks', 'administer themes'));
     $this->drupalLogin($admin_user);
 
-    // Ensure the block admin page cannot be accessed for a disabled theme.
+    // Ensure that access to block admin page is denied when theme is disabled.
     $this->drupalGet('admin/structure/block/list/bartik');
-    $this->assertResponse(404);
+    $this->assertResponse(403);
 
     // Enable admin theme and confirm that tab is accessible.
     theme_enable(array('bartik'));
diff --git a/core/modules/system/config/system.theme.yml b/core/modules/system/config/system.theme.yml
index e88d701..a1cbfa5 100644
--- a/core/modules/system/config/system.theme.yml
+++ b/core/modules/system/config/system.theme.yml
@@ -1,4 +1,3 @@
 admin: ''
-enabled:
-  stark: 0
-default: stark
+enabled: {}
+default: ''
diff --git a/core/modules/system/lib/Drupal/system/Controller/ThemeController.php b/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
index 7f1ad47..2fc246d 100644
--- a/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
+++ b/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
@@ -32,11 +32,12 @@ class ThemeController extends ControllerBase {
    */
   public function disable(Request $request) {
     $theme = $request->get('theme');
+    $theme_handler = \Drupal::service('theme_handler');
     $config = $this->config('system.theme');
 
     if (isset($theme)) {
       // Get current list of themes.
-      $themes = list_themes();
+      $themes = $theme_handler->listInfo();
 
       // Check if the specified theme is one recognized by the system.
       if (!empty($themes[$theme])) {
@@ -45,7 +46,7 @@ public function disable(Request $request) {
           drupal_set_message(t('%theme is the default theme and cannot be disabled.', array('%theme' => $themes[$theme]->info['name'])), 'error');
         }
         else {
-          theme_disable(array($theme));
+          $theme_handler->disable(array($theme));
           drupal_set_message(t('The %theme theme has been disabled.', array('%theme' => $themes[$theme]->info['name'])));
         }
       }
@@ -74,11 +75,11 @@ public function disable(Request $request) {
    */
   public function enable(Request $request) {
     $theme = $request->get('theme');
+    $theme_handler = \Drupal::service('theme_handler');
 
     if (isset($theme)) {
-      if (drupal_get_path('theme', $theme)) {
-        theme_enable(array($theme));
-        $themes = list_themes();
+      if ($theme_handler->enable(array($theme))) {
+        $themes = $theme_handler->listInfo();
         drupal_set_message(t('The %theme theme has been enabled.', array('%theme' => $themes[$theme]->info['name'])));
       }
       else {
diff --git a/core/modules/system/lib/Drupal/system/Tests/Extension/ThemeInstallTest.php b/core/modules/system/lib/Drupal/system/Tests/Extension/ThemeInstallTest.php
new file mode 100644
index 0000000..01d2af1
--- /dev/null
+++ b/core/modules/system/lib/Drupal/system/Tests/Extension/ThemeInstallTest.php
@@ -0,0 +1,74 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Extension\ThemeInstallTest.
+ */
+
+namespace Drupal\system\Tests\Extension;
+
+use Drupal\simpletest\DrupalUnitTestBase;
+
+/**
+ * Tests installing, enabling, disabling, and uninstalling of themes.
+ */
+class ThemeInstallTest extends DrupalUnitTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('system');
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Theme installation',
+      'description' => 'Tests installing, enabling, disabling, and uninstalling of themes.',
+      'group' => 'Extension',
+    );
+  }
+
+  function setUp() {
+    parent::setUp();
+    $this->installConfig(array('system'));
+  }
+
+  /**
+   * Tests enabling and disabling of themes.
+   */
+  function testEnableDisable() {
+    // Verify that no theme is installed/enabled/disabled by default.
+    $this->assertFalse($this->themeConfig()->get('enabled'));
+    $this->assertFalse($this->themeDisabledConfig()->get());
+    $this->assertFalse($this->themeHandler()->listInfo());
+  }
+
+  /**
+   * Returns the theme handler service.
+   *
+   * @return \Drupal\Core\Extension\ThemeHandlerInterface
+   */
+  protected function themeHandler() {
+    return $this->container->get('theme_handler');
+  }
+
+  /**
+   * Returns the system.theme config object.
+   *
+   * @return \Drupal\Core\Config\Config
+   */
+  protected function themeConfig() {
+    return $this->container->get('config.factory')->get('system.theme');
+  }
+
+  /**
+   * Returns the system.theme.disabled config object.
+   *
+   * @return \Drupal\Core\Config\Config
+   */
+  protected function themeDisabledConfig() {
+    return $this->container->get('config.factory')->get('system.theme.disabled');
+  }
+
+}
diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTest.php
index 0f17091..9d34007 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/ThemeTest.php
@@ -223,7 +223,7 @@ function testListThemes() {
    * Test the theme_get_setting() function.
    */
   function testThemeGetSetting() {
-    theme_enable(array('test_subtheme'));
+    \Drupal::service('theme_handler')->enable(array('test_subtheme'));
     $GLOBALS['theme_key'] = 'test_theme';
     $this->assertIdentical(theme_get_setting('theme_test_setting'), 'default value', 'theme_get_setting() uses the default theme automatically.');
     $this->assertNotEqual(theme_get_setting('subtheme_override', 'test_basetheme'), theme_get_setting('subtheme_override', 'test_subtheme'), 'Base theme\'s default settings values can be overridden by subtheme.');
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index 2cb14f5..81726b2 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -18,15 +18,14 @@ 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 (drupal_get_path('theme', $theme)) {
+    // Or try to enable the theme.
+    if (isset($themes[$theme]) || \Drupal::service('theme_handler')->enable(array($theme))) {
       $themes = list_themes();
-      // Enable the theme if it is currently disabled.
-      if (!isset($themes[$theme])) {
-        \Drupal::service('theme_handler')->enable(array($theme));
-        $themes = list_themes();
-      }
+
       // Set the default theme.
       \Drupal::config('system.theme')
         ->set('default', $theme)
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index fce3816..a53d196 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -1364,7 +1364,6 @@ function system_get_info($type, $name = NULL) {
     }
   }
   else {
-    // @todo Migrate theme info to ModuleInfo implementation.
     $list = system_list($type);
     foreach ($list as $shortname => $item) {
       if (!empty($item->status)) {
@@ -1509,48 +1508,30 @@ function system_rebuild_module_data() {
 }
 
 /**
- * Helper function to scan and collect theme .info.yml data and their engines.
- *
- * @return \Drupal\Core\Extension\Extension[]
- *   An associative array of themes information.
- *
- * @see \Drupal\Core\Extension\ThemeHandlerInterface::rebuildThemeData()
- *
- * @deprecated in Drupal 8.x-dev, will be removed before Drupal 8.0.
- *   Use \Drupal::service('theme_handler')->rebuildThemeData().
- */
-function _system_rebuild_theme_data() {
-  return \Drupal::service('theme_handler')->rebuildThemeData();
-}
-
-/**
  * Rebuild, save, and return data about all currently available themes.
  *
  * @return \Drupal\Core\Extension\Extension[]
  *   Array of all available themes and their data.
  */
 function system_rebuild_theme_data() {
-  $themes = _system_rebuild_theme_data();
+  $themes = \Drupal::service('theme_handler')->rebuildThemeData();
   ksort($themes);
-  // @todo This function has no business in determining/setting the status of
-  //   a theme, but various other functions expect it to return themes with a
-  //   $status property. system_list() stores the return value of this function
-  //   in state, and ensures to set/override the $status property for each theme
-  //   based on the current config. Remove this code when themes have a proper
-  //   installation status.
-  // @see http://drupal.org/node/1067408
+
   // Add human-readable name and status.
   $enabled_themes = (array) \Drupal::config('system.theme')->get('enabled');
   $files = array();
   foreach ($themes as $name => $theme) {
-    $theme->status = (int) isset($enabled_themes[$name]);
     $files[$name] = $theme->getPathname();
+    if (!isset($enabled_themes[$name])) {
+      unset($themes[$name]);
+      continue;
+    }
+    $theme->status = 1;
   }
-  // Set up dependencies.
+  // Build dependencies.
   $themes = \Drupal::moduleHandler()->buildModuleDependencies($themes);
 
   // Replace last known theme data state.
-  // @todo Obsolete with proper installation status for themes.
   \Drupal::state()->set('system.theme.data', $themes);
 
   // Store filenames to allow system_list() and drupal_get_filename() to
@@ -1597,9 +1578,10 @@ function system_region_list($theme, $show = REGIONS_ALL) {
     $theme = $themes[$theme];
   }
   $list = array();
+  $info = $theme->info;
   // If requested, suppress hidden regions. See block_admin_display_form().
-  foreach ($theme->info['regions'] as $name => $label) {
-    if ($show == REGIONS_ALL || !isset($theme->info['regions_hidden']) || !in_array($name, $theme->info['regions_hidden'])) {
+  foreach ($info['regions'] as $name => $label) {
+    if ($show == REGIONS_ALL || !isset($info['regions_hidden']) || !in_array($name, $info['regions_hidden'])) {
       $list[$name] = t($label);
     }
   }