reverted:
--- b/core/modules/system/src/Tests/Menu/MenuRouterTest.php
+++ a/core/modules/system/src/Tests/Menu/MenuRouterTest.php
@@ -306,6 +306,7 @@
$this->drupalGet('menu-test/theme-callback/use-stark-theme');
$this->assertText('Active theme: stark. Actual theme: stark.', 'The theme negotiation system uses an optional theme once it has been installed.');
+ $this->assertRaw('stark/css/layout.css', "The optional theme's CSS appears on the page.");
$theme_handler->uninstall(array('stark'));
}
diff -u b/core/themes/stark/stark.info.yml b/core/themes/stark/stark.info.yml
--- b/core/themes/stark/stark.info.yml
+++ b/core/themes/stark/stark.info.yml
@@ -3,4 +3,6 @@
-description: 'An intentionally plain theme with no styling to demonstrate default Drupal’s HTML and CSS. Learn how to build a custom theme from Stark in the Theming Guide.'
+description: 'An intentionally plain theme with almost no styling to demonstrate default Drupal’s HTML and CSS. Learn how to build a custom theme from Stark in the Theming Guide.'
package: Core
version: VERSION
core: 8.x
+libraries:
+ - stark/global-styling
reverted:
--- /dev/null
+++ a/core/themes/stark/stark.libraries.yml
@@ -0,0 +1,5 @@
+global-styling:
+ version: VERSION
+ css:
+ base:
+ css/layout.css: {}