Move Singleton and related structs to namespace base

chrome/browser/engagement/site_engagement_service_factory.cc

 // 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.
 
 #include "chrome/browser/engagement/site_engagement_service_factory.h"
 
 #include "chrome/browser/engagement/site_engagement_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 
 // static
 SiteEngagementService* SiteEngagementServiceFactory::GetForProfile(
     Profile* profile) {
   return static_cast<SiteEngagementService*>(
       GetInstance()->GetServiceForBrowserContext(profile, true));
 }
 
 // static
 SiteEngagementServiceFactory* SiteEngagementServiceFactory::GetInstance() {
-  return Singleton<SiteEngagementServiceFactory>::get();
+  return base::Singleton<SiteEngagementServiceFactory>::get();
 }
 
 SiteEngagementServiceFactory::SiteEngagementServiceFactory()
     : BrowserContextKeyedServiceFactory(
           "SiteEngagementService",
           BrowserContextDependencyManager::GetInstance()) {
 }
 
 SiteEngagementServiceFactory::~SiteEngagementServiceFactory() {
 }
 
 bool SiteEngagementServiceFactory::ServiceIsNULLWhileTesting() const {
   return true;
 }
 
 KeyedService* SiteEngagementServiceFactory::BuildServiceInstanceFor(
     content::BrowserContext* profile) const {
   return new SiteEngagementService(static_cast<Profile*>(profile));
 }