Move Singleton and related structs to namespace base

chrome/browser/ui/app_list/start_page_service_factory.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_UI_APP_LIST_START_PAGE_SERVICE_FACTORY_H_
 #define CHROME_BROWSER_UI_APP_LIST_START_PAGE_SERVICE_FACTORY_H_
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class Profile;
 
 namespace app_list {
 class StartPageService;
 
 // Singleton factory to create StartPageService.
 class StartPageServiceFactory : public BrowserContextKeyedServiceFactory {
  public:
   // Gets or creates the instance of StartPageService for |profile|. May return
   // nullptr.
   static StartPageService* GetForProfile(Profile* profile);
 
   // Gets the singleton instance of this factory.
   static StartPageServiceFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<StartPageServiceFactory>;
+  friend struct base::DefaultSingletonTraits<StartPageServiceFactory>;
 
   StartPageServiceFactory();
   ~StartPageServiceFactory() override;
 
   // BrowserContextKeyedServiceFactory overrides:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
   content::BrowserContext* GetBrowserContextToUse(
     content::BrowserContext* context) const override;
 
   DISALLOW_COPY_AND_ASSIGN(StartPageServiceFactory);
 };
 
 }  // namespace app_list
 
 #endif  // CHROME_BROWSER_UI_APP_LIST_START_PAGE_SERVICE_FACTORY_H_