diff --git a/core/modules/system/src/Controller/AssetControllerBase.php b/core/modules/system/src/Controller/AssetControllerBase.php
index 9544605..439da7c 100644
--- a/core/modules/system/src/Controller/AssetControllerBase.php
+++ b/core/modules/system/src/Controller/AssetControllerBase.php
@@ -167,8 +167,9 @@ public function deliver(Request $request, $file_name) {
     if ($request->query->has('already_loaded')) {
       $attached_assets->setAlreadyLoadedLibraries($request->query->get('already_loaded'));
     }
-    $group = $this->getGroup($attached_assets, $group_delta, $request);
-    $key = $this->generateHash($group);
+    $groups = $this->getGroups($attached_assets, $request);
+    $key = $this->generateHash($groups);
+    $group = $this->getGroup($groups, $group_delta);
     $hash = $file_parts[2];
 
     // The hash from the library definitions in code may not match the hash from
@@ -217,7 +218,7 @@ public function deliver(Request $request, $file_name) {
       $data = $this->optimizer->optimizeGroup($group);
       // Dump the optimized CSS for this group into an aggregate file.
       if ($match) {
-        $uri = $this->dumper->dump($data, $this->assetType, $uri);
+        $uri = $this->dumper->dumpToUri($data, $this->assetType, $uri);
       }
       $headers = [
         'Content-Type' => $this->contentType,
@@ -233,17 +234,30 @@ public function deliver(Request $request, $file_name) {
   }
 
   /**
-   * Get assets of a certain type given attached assets.
+   * Get a group.
    *
-   * @param AttachedAssetsInterface $attached_assets
-   *   An object implementing AttachedAssetsInterface
+   * @param array $groups
+   *   An array of asset groups
    *  @param int $group_delta
    *    The group delta.
-   *  @param Symfony\Component\HttpFoundation\Request
-   *    The current request.
    *
    * @return []
    *   The correct asset group matching $group_delta.
    */
-  abstract protected function getGroup(AttachedAssetsInterface $attached_assets, $group_delta, $request);
+  protected function getGroup($groups, $group_delta) {
+    if (isset($groups[$group_delta])) {
+      return $groups[$group_delta];
+    }
+    throw new BadRequestHttpException('Invalid filename.');
+  }
+
+  /**
+   * Get grouped assets.
+   *
+   * @param Drupal\Core\Asset\AttachedAssetsInterface $attached_assets
+   *   The attached assets.
+   * @param Symfony\Component\HttpFoundation\Request $request
+   *   The current request.
+   */
+  abstract protected function getGroups(AttachedAssetsInterface $attached_assets, Request $request);
 }
diff --git a/core/modules/system/src/Controller/CssAssetController.php b/core/modules/system/src/Controller/CssAssetController.php
index cab803c..32fdcf6 100644
--- a/core/modules/system/src/Controller/CssAssetController.php
+++ b/core/modules/system/src/Controller/CssAssetController.php
@@ -3,7 +3,7 @@
 namespace Drupal\system\Controller;
 
 use Symfony\Component\DependencyInjection\ContainerInterface;
-use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
+use Symfony\Component\HttpFoundation\Request;
 
 use Drupal\Core\Asset\AttachedAssetsInterface;
 use Drupal\Core\Asset\AssetGroupSetHashTrait;
@@ -41,15 +41,9 @@ public static function create(ContainerInterface $container) {
   /**
    * {@inheritdoc}
    */
-  protected function getGroup(AttachedAssetsInterface $attached_assets, $group_delta, $request) {
+  protected function getGroups(AttachedAssetsInterface $attached_assets, Request $request) {
     $assets = $this->assetResolver->getCssAssets($attached_assets, FALSE);
-
-    // Group the assets.
-    $groups = $this->grouper->group($assets);
-    if (!isset($groups[$group_delta])) {
-      throw new BadRequestHttpException('Invalid filename.');
-    }
-    return $groups[$group_delta];
+    return $this->grouper->group($assets);
   }
 
 }
diff --git a/core/modules/system/src/Controller/JsAssetController.php b/core/modules/system/src/Controller/JsAssetController.php
index 138f4a4..78ecfa3 100644
--- a/core/modules/system/src/Controller/JsAssetController.php
+++ b/core/modules/system/src/Controller/JsAssetController.php
@@ -3,7 +3,7 @@
 namespace Drupal\system\Controller;
 
 use Symfony\Component\DependencyInjection\ContainerInterface;
-use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
+use Symfony\Component\HttpFoundation\Request;
 
 use Drupal\Core\Asset\AttachedAssetsInterface;
 use Drupal\Core\Asset\AssetGroupSetHashTrait;
@@ -42,7 +42,7 @@ public static function create(ContainerInterface $container) {
   /**
    * {@inheritdoc}
    */
-  protected function getGroup(AttachedAssetsInterface $attached_assets, $group_delta, $request) {
+  protected function getGroups(AttachedAssetsInterface $attached_assets, Request $request) {
     // The header and footer scripts are two distinct sets of asset groups. The
     // $group_key is not sufficient to find the group, we also need to locate it
     // within either the header or footer set.
@@ -55,13 +55,7 @@ protected function getGroup(AttachedAssetsInterface $attached_assets, $group_del
     // While the asset resolver will find setting, these are never aggregated,
     // so filter them out. Settings are always in the header.
     unset($assets['drupalSettings']);
-    // Group the assets.
-    $groups = $this->grouper->group($assets);
-    if (!isset($groups[$group_delta])) {
-      throw new BadRequestHttpException('Invalid filename.');
-    }
-    $group = $groups[$group_delta];
-    return $group;
+    return $this->grouper->group($assets);
   }
 
 }