Move Singleton and related structs to namespace base

chrome/browser/sync/sync_error_notifier_factory_ash.h

 // 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.
 
 #ifndef CHROME_BROWSER_SYNC_SYNC_ERROR_NOTIFIER_FACTORY_ASH_H_
 #define CHROME_BROWSER_SYNC_SYNC_ERROR_NOTIFIER_FACTORY_ASH_H_
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class SyncErrorNotifier;
 class Profile;
 
 // Singleton that owns all SyncErrorNotifiers and associates them with
 // Profiles. Listens for the Profile's destruction notification and cleans up
 // the associated SyncErrorNotifier.
 class SyncErrorNotifierFactory : public BrowserContextKeyedServiceFactory {
  public:
   // Returns the instance of SyncErrorNotifier associated with this profile,
   // creating one if none exists and the shell exists.
   static SyncErrorNotifier* GetForProfile(Profile* profile);
 
   // Returns an instance of the SyncErrorNotifierFactory singleton.
   static SyncErrorNotifierFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<SyncErrorNotifierFactory>;
+  friend struct base::DefaultSingletonTraits<SyncErrorNotifierFactory>;
 
   SyncErrorNotifierFactory();
   ~SyncErrorNotifierFactory() override;
 
   // BrowserContextKeyedServiceFactory:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* profile) const override;
 
   DISALLOW_COPY_AND_ASSIGN(SyncErrorNotifierFactory);
 };
 
 #endif  // CHROME_BROWSER_SYNC_SYNC_ERROR_NOTIFIER_FACTORY_ASH_H_