Move Singleton and related structs to namespace base

chrome/browser/engagement/site_engagement_service_factory.h

 // Copyright 2015 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_ENGAGEMENT_SITE_ENGAGEMENT_SERVICE_FACTORY_H_
 #define CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_SERVICE_FACTORY_H_
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class Profile;
 class SiteEngagementService;
 
 // Singleton that owns all SiteEngagementServices and associates them with
 // Profiles. Listens for the Profile's destruction notification and cleans up
 // the associated SiteEngagementService.
 //
 // The default factory behavior is suitable for this factory as:
 // * there should be no site engagement tracking in incognito
 // * the site engagement service should be created lazily
 // * the site engagement service is needed in tests.
 class SiteEngagementServiceFactory : public BrowserContextKeyedServiceFactory {
  public:
   static SiteEngagementService* GetForProfile(Profile* profile);
 
   static SiteEngagementServiceFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<SiteEngagementServiceFactory>;
+  friend struct base::DefaultSingletonTraits<SiteEngagementServiceFactory>;
 
   SiteEngagementServiceFactory();
   ~SiteEngagementServiceFactory() override;
 
   // KeyedServiceBaseFactory:
   bool ServiceIsNULLWhileTesting() const override;
 
   // BrowserContextKeyedServiceFactory:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* profile) const override;
 
   DISALLOW_COPY_AND_ASSIGN(SiteEngagementServiceFactory);
 };
 
 #endif  // CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_SERVICE_FACTORY_H_