diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index de8131b..720f806 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1203,7 +1203,7 @@ function template_preprocess(&$variables, $hook, $info) {
   $render_element_type = isset($info['render element']) ? $info['render element'] : NULL;
 
   $themeManager = \Drupal::service('theme.manager');
-  $variables += $themeManager->getDefaultTemplateVariables($render_element_type);
+  $variables += $themeManager->getDefaultTemplateVariables($render_element_type, $variables);
 }
 
 /**
diff --git a/core/lib/Drupal/Core/Theme/Registry.php b/core/lib/Drupal/Core/Theme/Registry.php
index a8a0ae0..f389990 100644
--- a/core/lib/Drupal/Core/Theme/Registry.php
+++ b/core/lib/Drupal/Core/Theme/Registry.php
@@ -511,7 +511,6 @@ protected function processExtension(array &$cache, $name, $type, $theme, $path)
         if (!isset($info['preprocess functions']) || !is_array($info['preprocess functions'])) {
           $info['preprocess functions'] = array();
           $prefixes = array();
-
           if ($type == 'module') {
             // Add template_preprocess_HOOK functions.
             if (function_exists('template_preprocess_' . $hook)) {
diff --git a/core/lib/Drupal/Core/Theme/ThemeManager.php b/core/lib/Drupal/Core/Theme/ThemeManager.php
index 7bf0e30..7f96d32 100644
--- a/core/lib/Drupal/Core/Theme/ThemeManager.php
+++ b/core/lib/Drupal/Core/Theme/ThemeManager.php
@@ -3,12 +3,12 @@
 namespace Drupal\Core\Theme;
 
 use Drupal\Component\Render\MarkupInterface;
+use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Render\Markup;
 use Drupal\Core\Routing\RouteMatchInterface;
 use Drupal\Core\Routing\StackedRouteMatchInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Template\Attribute;
-use Drupal\Component\Utility\NestedArray;
 
 /**
  * Provides the default implementation of a theme manager.
@@ -284,8 +284,16 @@ public function render($hook, array $variables) {
     }
 
     // Set default variables before preprocess hooks.
-    $render_element_type = isset($info['render element']) ? $info['render element'] : NULL;
-    $variables += $this->getDefaultTemplateVariables($render_element_type);
+    $variables += $this->getDefaultTemplateVariables();
+
+    // Merge element #attributes into $default_variables['attributes'] if they
+    // exist in render_element.
+    if (isset($element['#attributes'])) {
+      $variables['attributes'] = NestedArray::mergeDeep(
+        $variables['attributes'],
+        $element['#attributes']
+      );
+    }
 
     // Invoke preprocess hooks.
     // By default $info['preprocess functions'] should always be set, but it's
@@ -459,37 +467,29 @@ public function alter($type, &$data, &$context1 = NULL, &$context2 = NULL) {
   /**
    * {@inheritdoc}
    */
-  public function getDefaultTemplateVariables($render_element_type) {
+  public function getDefaultTemplateVariables() {
     static $drupal_static_fast;
     if (!isset($drupal_static_fast)) {
-      $drupal_static_fast['default_variables'] = &drupal_static('getDefaultTemplateVariables');
+      $drupal_static_fast['default_variables'] = &drupal_static(__METHOD__);
     }
     $default_variables = &$drupal_static_fast['default_variables'];
-    if(!isset($default_variables)) {
+    if (!isset($default_variables)) {
       // Variables that don't depend on a database connection.
-      $default_variables = array(
-        'attributes' => array(),
-        'title_attributes' => array(),
-        'content_attributes' => array(),
-        'title_prefix' => array(),
-        'title_suffix' => array(),
+      $default_variables = [
+        'attributes' => [],
+        'title_attributes' => [],
+        'content_attributes' => [],
+        'title_prefix' => [],
+        'title_suffix' => [],
         'db_is_active' => !defined('MAINTENANCE_MODE'),
         'is_admin' => FALSE,
         'logged_in' => FALSE,
-      );
+      ];
 
       // Give modules a chance to alter default template variables.
       \Drupal::moduleHandler()->alter('template_preprocess_default_variables', $default_variables);
       // Tell all templates where they are located.
-      $default_variables['directory'] = \Drupal::theme()->getActiveTheme()->getPath();
-    }
-    // Merge element #attributes into $default_variables['attributes'] if they
-    // exist in render_element.
-    if (isset($default_variables[$render_element_type]['#attributes'])) {
-      $default_variables['attributes'] = NestedArray::mergeDeep(
-        $default_variables['attributes'],
-        $default_variables[$render_element_type]['#attributes']
-      );
+      $default_variables['directory'] = $this->getActiveTheme()->getPath();
     }
     return $default_variables;
   }
diff --git a/core/lib/Drupal/Core/Theme/ThemeManagerInterface.php b/core/lib/Drupal/Core/Theme/ThemeManagerInterface.php
index 74bf3e8..42bf65c 100644
--- a/core/lib/Drupal/Core/Theme/ThemeManagerInterface.php
+++ b/core/lib/Drupal/Core/Theme/ThemeManagerInterface.php
@@ -153,13 +153,9 @@ public function alterForTheme(ActiveTheme $theme, $type, &$data, &$context1 = NU
    * See the @link themeable Default theme implementations topic @endlink for
    * details.
    *
-   * @see template_preprocess()
-   *
-   * @param string $render_element_type
-   *   The type of the element to render. E.g. 'html', 'page', 'element',
-   *   'elements, 'form'...
-   * @return
+   * @return array
    *   An array of default template variables.
    */
-  public function getDefaultTemplateVariables($render_element_type);
+  public function getDefaultTemplateVariables();
+
 }