Issue #2095311 by Wim Leers: Remove drupal_add_css() from update.module.

core/modules/update/update.manager.inc

@@ -82,7 +82,7 @@ function update_manager_update_form($form, $form_state = array(), $context) {
     return $form;
   }
 
-  $form['#attached']['css'][] = drupal_get_path('module', 'update') . '/css/update.admin.css';
+  $form['#attached']['library'][] = array('update', 'drupal.update.admin');
 
   // This will be a nested array. The first key is the kind of project, which
   // can be either 'enabled', 'disabled', 'manual' (projects which require

core/modules/update/update.module

@@ -144,6 +144,23 @@ function update_page_build() {
   }
 }
 
+/**
+ * Implements hook_library_info().
+ */
+function update_library_info() {
+  $path = drupal_get_path('module', 'update');
+  $libraries['drupal.update.admin'] = array(
+    'title' => 'Update administration UI',
+    'website' => '',
+    'version' => \Drupal::VERSION,
+    'css' => array(
+      $path . '/css/update.admin.css' => array(),
+    ),
+  );
+
+  return $libraries;
+}
+
 /**
  * Implements hook_menu().
  */

core/modules/update/update.report.inc

@@ -293,7 +293,16 @@ function theme_update_report($variables) {
       $output .= drupal_render($table);
     }
   }
-  drupal_add_css(drupal_get_path('module', 'update') . '/css/update.admin.css');
+
+  $assets = array(
+    '#attached' => array(
+      'library' => array(
+        array('update', 'drupal.update.admin'),
+      ),
+    )
+  );
+  drupal_render($assets);
+
   return $output;
 }