Issue #2380605 by emma.maria, lauriii: Bartik layout broken

core/modules/system/src/Tests/Theme/ThemeInfoTest.php

@@ -99,13 +99,13 @@ public function testChanges() {
     $active_theme = $this->themeManager->getActiveTheme();
     // Make sure we are not testing the wrong theme.
     $this->assertEqual('test_theme', $active_theme->getName());
-    $this->assertEqual([], $active_theme->getLibraries());
+    $this->assertEqual(['classy/base'], $active_theme->getLibraries());
 
     // @see theme_test_system_info_alter()
     $this->state->set('theme_test.modify_info_files', TRUE);
     drupal_flush_all_caches();
     $active_theme = $this->themeManager->getActiveTheme();
-    $this->assertEqual(['core/backbone'], $active_theme->getLibraries());
+    $this->assertEqual(['classy/base', 'core/backbone'], $active_theme->getLibraries());
   }
 
 }

core/themes/classy/classy.info.yml

@@ -5,6 +5,5 @@ package: Core
 version: VERSION
 core: 8.x
 
-stylesheets:
-  all:
-    - css/layout.css
+libraries:
+  - classy/base

core/themes/classy/classy.libraries.yml

+base:
+  version: VERSION
+  css:
+    theme:
+      css/layout.css: {}