Move Singleton and related structs to namespace base

chrome/browser/sync/profile_sync_service_factory.h

 // Copyright (c) 2012 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.
 
 #ifndef CHROME_BROWSER_SYNC_PROFILE_SYNC_SERVICE_FACTORY_H_
 #define CHROME_BROWSER_SYNC_PROFILE_SYNC_SERVICE_FACTORY_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
@@ skipping 11 matching lines @@
   static bool HasProfileSyncService(Profile* profile);
 
   // Convenience method that returns the ProfileSyncService as a
   // sync_driver::SyncService.
   static sync_driver::SyncService* GetSyncServiceForBrowserContext(
       content::BrowserContext* context);
 
   static ProfileSyncServiceFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<ProfileSyncServiceFactory>;
+  friend struct base::DefaultSingletonTraits<ProfileSyncServiceFactory>;
 
   ProfileSyncServiceFactory();
   ~ProfileSyncServiceFactory() override;
 
   // BrowserContextKeyedServiceFactory:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
 };
 
 #endif  // CHROME_BROWSER_SYNC_PROFILE_SYNC_SERVICE_FACTORY_H_