diff --git a/core/modules/layout/layouts/static/twocol/twocol.yml b/core/modules/layout/layouts/static/twocol/twocol.yml
index 6362669..5e19696 100644
--- a/core/modules/layout/layouts/static/twocol/twocol.yml
+++ b/core/modules/layout/layouts/static/twocol/twocol.yml
@@ -1,7 +1,8 @@
 title: Two column
 category: Columns: 2
 template: twocol
-css: twocol.css
+stylesheets:
+  - twocol.css
 regions:
   left: 'Left side'
   right: 'Right side'
diff --git a/core/modules/layout/lib/Drupal/layout/Plugin/layout/layout/StaticLayout.php b/core/modules/layout/lib/Drupal/layout/Plugin/layout/layout/StaticLayout.php
index 581d38b..e300dc3 100644
--- a/core/modules/layout/lib/Drupal/layout/Plugin/layout/layout/StaticLayout.php
+++ b/core/modules/layout/lib/Drupal/layout/Plugin/layout/layout/StaticLayout.php
@@ -43,60 +43,45 @@ public function getRegions() {
   }
 
   /**
-   * Add the CSS files associated with this layout to the page.
+   * Returns the list of CSS files associated with this layout.
    */
-  public function getCssFiles() {
+  public function getStylesheetFiles() {
     $definition = $this->getDefinition();
-    $files = $definition['css'];
-    if (is_string($files)) {
-      $files = array($files);
-    }
-    return $files;
+    return $definition['stylesheets'];
   }
 
   /**
-   * Add the administrative CSS files associated with this layout to the page.
+   * Returns the list of administrative CSS files associated with this layout.
    */
-  public function getAdminCssFiles() {
+  public function getAdminStylesheetFiles() {
     $definition = $this->getDefinition();
     // Fall back on regular CSS for the admin page if admin CSS not provided.
-    $files = isset($definition['admin css']) ? $definition['admin css'] : $definition['css'];
-    if (is_string($files)) {
-      $files = array($files);
-    }
-    return $files;
+    return isset($definition['admin stylesheets']) ? $definition['admin stylesheets'] : $definition['stylesheets'];
   }
 
   /**
-   * Add the JS files associated with this layout to the page.
+   * Returns the list of JS files associated with this layout.
    */
-  public function getJsFiles() {
+  public function getScriptFiles() {
     $definition = $this->getDefinition();
-    if (isset($definition['js']))  {
-      $files = $definition['js'];
-      if (is_string($files)) {
-        $files = array($files);
-      }
-      return $files;
+    if (isset($definition['scripts']))  {
+      return $definition['scripts'];
     }
     return array();
   }
 
   /**
-   * Add the admin JS files associated with this layout to the page.
+   * Returns the list of administrative JS files associated with this layout.
    */
-  public function getAdminJsFiles() {
+  public function getAdminScriptFiles() {
     $definition = $this->getDefinition();
     $files = array();
-    if (isset($definition['admin js'])) {
-      $files = $definition['admin js'];
+    if (isset($definition['admin scripts'])) {
+      $files = $definition['admin scripts'];
     }
-    elseif (isset($definition['js'])) {
+    elseif (isset($definition['scripts'])) {
       // Fall back on regular JS for the admin page if admin JS not provided.
-      $files = $definition['js'];
-    }
-    if (is_string($files)) {
-      $files = array($files);
+      $files = $definition['scripts'];
     }
     return $files;
   }
@@ -108,7 +93,7 @@ public function renderLayout($admin = FALSE) {
     $definition = $this->getDefinition();
 
     // Assemble a render array with the regions and attached CSS/JS.
-    $render = array(
+    $build = array(
       '#theme' => $definition['theme'],
       '#content' => array(),
     );
@@ -118,30 +103,30 @@ public function renderLayout($admin = FALSE) {
       // @todo This is just stub code to fill in regions with stuff for now.
       // When blocks are related to layouts and not themes, we can make this
       // really be filled in with blocks.
-      $render['#content'][$region] = '<h3>' . $title . '</h3>';
+      $build['#content'][$region] = '<h3>' . $title . '</h3>';
     }
 
     // Fill in attached CSS and JS files based on metadata.
     if (!$admin) {
-      $render['#attached'] = array(
-        'css' => $this->getCssFiles(),
-        'js' => $this->getJsFiles(),
+      $build['#attached'] = array(
+        'css' => $this->getStylesheetFiles(),
+        'js' => $this->getScriptFiles(),
       );
     }
     else {
-      $render['#attached'] = array(
-        'css' => $this->getAdminCssFiles(),
-        'js' => $this->getAdminJsFiles(),
+      $build['#attached'] = array(
+        'css' => $this->getAdminStylesheetFiles(),
+        'js' => $this->getAdminScriptFiles(),
       );
     }
 
     // Include the path of the definition in all CSS and JS files.
     foreach (array('css', 'js') as $type) {
-      foreach ($render['#attached'][$type] as &$filename) {
+      foreach ($build['#attached'][$type] as &$filename) {
         $filename = $definition['path'] . '/' . $filename;
       }
     }
 
-    return drupal_render($render);
+    return drupal_render($build);
   }
 }
diff --git a/core/modules/layout/tests/themes/layout_test_theme/layouts/static/page/page.yml b/core/modules/layout/tests/themes/layout_test_theme/layouts/static/page/page.yml
index 68bb478..e44950a 100644
--- a/core/modules/layout/tests/themes/layout_test_theme/layouts/static/page/page.yml
+++ b/core/modules/layout/tests/themes/layout_test_theme/layouts/static/page/page.yml
@@ -1,7 +1,8 @@
 title: Layout test page
 category: Other
 template: test-layout
-css: page.css
+stylesheets:
+  - page.css
 regions:
   header: 'Header'
   help: 'Help'