Bring up of the enhanced bookmarks cluster service.

components/enhanced_bookmarks/pref_names.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-namespace invalidation {
+#include "components/enhanced_bookmarks/pref_names.h"
+
+namespace enhanced_bookmarks {
 namespace prefs {
 
-extern const char kInvalidatorClientId[];
-
-extern const char kInvalidatorInvalidationState[];
-
-extern const char kInvalidatorSavedInvalidations[];
-
+const char kBookmarkClusters[] =
+    "enhanced_bookmarks_component.bookmark_clusters";
 }  // namespace prefs
-}  // namespace invalidation
+}  // namespace enhanced_bookmarks