Issue #1620114 by Rob Loach, sun: Explicitly register \Drupal\Component and...

Issue #1620114 by Rob Loach, sun: Explicitly register \Drupal\Component and \Drupal\Core to increase class lookup performance.

core/includes/bootstrap.inc

@@ -3125,6 +3125,15 @@ function drupal_classloader() {
         break;
     }
 
+    // Register explicit namespaces for Drupal core.
+    // The majority of namespaces that need to be resolved are from Drupal core,
+    // so registering/setting them before vendor libraries saves a few
+    // additional cycles per class lookup.
+    $loader->registerNamespaces(array(
+      'Drupal\Core' => DRUPAL_ROOT . '/core/lib',
+      'Drupal\Component' => DRUPAL_ROOT . '/core/lib',
+    ));
+
     // Register namespaces for vendor libraries managed by Composer.
     $namespaces = require DRUPAL_ROOT . '/core/vendor/composer/autoload_namespaces.php';
     $prefixes = array();
@@ -3142,17 +3151,6 @@ function drupal_classloader() {
     $loader->registerPrefixes($prefixes);
     $loader->registerNamespaces($namespaces);
 
-    // Register the Drupal namespace for classes in core as a fallback.
-    // This allows to register additional namespaces within the Drupal namespace
-    // (e.g., for modules) and avoids an additional file_exists() on the Drupal
-    // core namespace, since the class loader can already determine the best
-    // namespace match based on a string comparison. It further allows modules
-    // to register/overload namespaces in Drupal core.
-    $loader->registerNamespaceFallbacks(array(
-      // All Drupal-namespaced code in core lives in /core/lib/Drupal.
-      'Drupal' => DRUPAL_ROOT . '/core/lib',
-    ));
-
     // Register the loader with PHP.
     $loader->register();
   }