Move Singleton and related structs to namespace base

chrome/browser/extensions/api/system_indicator/system_indicator_manager_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_EXTENSIONS_API_SYSTEM_INDICATOR_SYSTEM_INDICATOR_MANAGER_FACTORY_H__
 #define CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INDICATOR_SYSTEM_INDICATOR_MANAGER_FACTORY_H__
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class Profile;
 
 namespace extensions {
 class SystemIndicatorManager;
 
 // BrowserContextKeyedServiceFactory for each SystemIndicatorManager.
 class SystemIndicatorManagerFactory : public BrowserContextKeyedServiceFactory {
  public:
   static SystemIndicatorManager* GetForProfile(Profile* profile);
 
   static SystemIndicatorManagerFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<SystemIndicatorManagerFactory>;
+  friend struct base::DefaultSingletonTraits<SystemIndicatorManagerFactory>;
 
   SystemIndicatorManagerFactory();
   ~SystemIndicatorManagerFactory() override;
 
   // BrowserContextKeyedBaseFactory implementation.
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* profile) const override;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_SYSTEM_INDICATOR_SYSTEM_INDICATOR_MANAGER_FACTORY_H__