diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 207fdda..a113c25 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -271,7 +271,8 @@ function drupal_get_filename($type, $name, $filename = NULL) {
       }
     }
     // If still unknown, retrieve the file list prepared in state by
-    // system_rebuild_module_data() and system_rebuild_theme_data().
+    // system_rebuild_module_data() and
+    // ThemeHandlerInterface::rebuildThemeData().
     if (!isset($files[$type][$name]) && \Drupal::hasService('state')) {
       $files[$type] += \Drupal::state()->get('system.' . $type . '.files', array());
     }
diff --git a/core/includes/theme.maintenance.inc b/core/includes/theme.maintenance.inc
index e40498c..ea6ed1d 100644
--- a/core/includes/theme.maintenance.inc
+++ b/core/includes/theme.maintenance.inc
@@ -63,14 +63,11 @@ function _drupal_maintenance_theme() {
     }
   }
 
-  // Ensure that system.module is loaded.
-  if (!function_exists('system_rebuild_theme_data')) {
-    $module_handler = \Drupal::moduleHandler();
-    $module_handler->addModule('system', 'core/modules/system');
-    $module_handler->load('system');
-  }
+  $module_handler = \Drupal::moduleHandler();
+  $module_handler->addModule('system', 'core/modules/system');
+  $module_handler->load('system');
 
-  $themes = list_themes();
+  $themes = \Drupal::service('theme_handler')->listInfo();
 
   // If no themes are installed yet, or if the requested custom theme is not
   // installed, retrieve all available themes.
diff --git a/core/includes/update.inc b/core/includes/update.inc
index 510dc8c..46ab61b 100644
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -44,7 +44,7 @@ function update_check_incompatibility($name, $type = 'module') {
     // We need to do a full rebuild here to make sure the database reflects any
     // code changes that were made in the filesystem before the update script
     // was initiated.
-    $themes = system_rebuild_theme_data();
+    $themes = \Drupal::service('theme_handler')->rebuildThemeData();
     $modules = system_rebuild_module_data();
   }
 
diff --git a/core/lib/Drupal/Core/Updater/Theme.php b/core/lib/Drupal/Core/Updater/Theme.php
index b379325..ea853c8 100644
--- a/core/lib/Drupal/Core/Updater/Theme.php
+++ b/core/lib/Drupal/Core/Updater/Theme.php
@@ -76,7 +76,7 @@ public static function canUpdate($project_name) {
   public function postInstall() {
     // Update the theme info.
     clearstatcache();
-    system_rebuild_theme_data();
+    \Drupal::service('theme_handler')->rebuildThemeData();
   }
 
   /**
diff --git a/core/modules/locale/locale.compare.inc b/core/modules/locale/locale.compare.inc
index e131d99..efefa3b 100644
--- a/core/modules/locale/locale.compare.inc
+++ b/core/modules/locale/locale.compare.inc
@@ -126,7 +126,7 @@ function locale_translation_project_list() {
       'interface translation server pattern',
     );
     $module_data = _locale_translation_prepare_project_list(system_rebuild_module_data(), 'module');
-    $theme_data = _locale_translation_prepare_project_list(system_rebuild_theme_data(), 'theme');
+    $theme_data = _locale_translation_prepare_project_list(\Drupal::service('theme_handler')->rebuildThemeData(), 'theme');
     $project_info = new ProjectInfo();
     $project_info->processInfoList($projects, $module_data, 'module', TRUE, $additional_whitelist);
     $project_info->processInfoList($projects, $theme_data, 'theme', TRUE, $additional_whitelist);
diff --git a/core/modules/system/module.api.php b/core/modules/system/module.api.php
index 29a9bf3..ed08c8b 100644
--- a/core/modules/system/module.api.php
+++ b/core/modules/system/module.api.php
@@ -86,9 +86,9 @@ function hook_module_implements_alter(&$implementations, $hook) {
  * Alter the information parsed from module and theme .info.yml files
  *
  * This hook is invoked in _system_rebuild_module_data() and in
- * _system_rebuild_theme_data(). A module may implement this hook in order to
- * add to or alter the data generated by reading the .info.yml file with
- * \Drupal\Core\Extension\InfoParser.
+ * ThemeHandlerInterface::rebuildThemeData(). A module may implement this hook
+ * in order to add to or alter the data generated by reading the .info.yml file
+ * with \Drupal\Core\Extension\InfoParser.
  *
  * @param array $info
  *   The .info.yml file contents, passed by reference so that it can be altered.
diff --git a/core/modules/system/src/Tests/Extension/ModuleHandlerTest.php b/core/modules/system/src/Tests/Extension/ModuleHandlerTest.php
index 69f5627..5bd32c6 100644
--- a/core/modules/system/src/Tests/Extension/ModuleHandlerTest.php
+++ b/core/modules/system/src/Tests/Extension/ModuleHandlerTest.php
@@ -235,7 +235,7 @@ public function testModuleStreamWrappers() {
    */
   function testThemeMetaData() {
     // Generate the list of available themes.
-    $themes = system_rebuild_theme_data();
+    $themes = \Drupal::service('theme_handler')->rebuildThemeData();
     // Check that the mtime field exists for the bartik theme.
     $this->assertTrue(!empty($themes['bartik']->info['mtime']), 'The bartik.info.yml file modification time field is present.');
     // Use 0 if mtime isn't present, to avoid an array index notice.
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 0d41bba..8a57f77 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -737,7 +737,7 @@ function system_check_directory($form_element, FormStateInterface $form_state) {
  *   array is returned.
  *
  * @see system_rebuild_module_data()
- * @see system_rebuild_theme_data()
+ * @see ThemeHandlerInterface::rebuildThemeData()
  */
 function system_get_info($type, $name = NULL) {
   $info = array();
@@ -894,19 +894,6 @@ function system_rebuild_module_data() {
 }
 
 /**
- * Rebuild, save, and return data about all currently available themes.
- *
- * @return \Drupal\Core\Extension\Extension[]
- *   Array of all available themes and their data.
- *
- * @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();
-}
-
-/**
  * Returns an array of default theme features.
  */
 function _system_default_theme_features() {
diff --git a/core/modules/update/src/Tests/UpdateContribTest.php b/core/modules/update/src/Tests/UpdateContribTest.php
index 95e2b88..599a686 100644
--- a/core/modules/update/src/Tests/UpdateContribTest.php
+++ b/core/modules/update/src/Tests/UpdateContribTest.php
@@ -293,7 +293,7 @@ function testUpdateHiddenBaseTheme() {
     );
     \Drupal::config('update_test.settings')->set('system_info', $system_info)->save();
     $projects = update_get_projects();
-    $theme_data = system_rebuild_theme_data();
+    $theme_data = \Drupal::service('theme_handler')->rebuildThemeData();
     $project_info = new ProjectInfo();
     $project_info->processInfoList($projects, $theme_data, 'theme', TRUE);
 
diff --git a/core/modules/update/src/UpdateManager.php b/core/modules/update/src/UpdateManager.php
index 21cfe80..567cc0b 100644
--- a/core/modules/update/src/UpdateManager.php
+++ b/core/modules/update/src/UpdateManager.php
@@ -123,7 +123,7 @@ public function getProjects() {
       if (empty($this->projects)) {
         // Still empty, so we have to rebuild.
         $module_data = system_rebuild_module_data();
-        $theme_data = system_rebuild_theme_data();
+        $theme_data = \Drupal::service('theme_handler')->rebuildThemeData();
         $project_info = new ProjectInfo();
         $project_info->processInfoList($this->projects, $module_data, 'module', TRUE);
         $project_info->processInfoList($this->projects, $theme_data, 'theme', TRUE);