Move Singleton and related structs to namespace base

chrome/browser/notifications/notifier_state_tracker_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/notifications/notifier_state_tracker_factory.h"
 
 #include "chrome/browser/notifications/notification_permission_context_factory.h"
 #include "chrome/browser/notifications/notifier_state_tracker.h"
 #include "chrome/browser/profiles/incognito_helpers.h"
 #include "chrome/browser/profiles/profile.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 
 // static
 NotifierStateTracker*
 NotifierStateTrackerFactory::GetForProfile(Profile* profile) {
   return static_cast<NotifierStateTracker*>(
       GetInstance()->GetServiceForBrowserContext(profile, true));
 }
 
 // static
 NotifierStateTrackerFactory*
 NotifierStateTrackerFactory::GetInstance() {
-  return Singleton<NotifierStateTrackerFactory>::get();
+  return base::Singleton<NotifierStateTrackerFactory>::get();
 }
 
 NotifierStateTrackerFactory::NotifierStateTrackerFactory()
     : BrowserContextKeyedServiceFactory(
           "NotifierStateTracker",
           BrowserContextDependencyManager::GetInstance()) {
   DependsOn(NotificationPermissionContextFactory::GetInstance());
 }
 
 NotifierStateTrackerFactory::~NotifierStateTrackerFactory() {}
 
 KeyedService* NotifierStateTrackerFactory::BuildServiceInstanceFor(
     content::BrowserContext* profile) const {
   return new NotifierStateTracker(static_cast<Profile*>(profile));
 }
 
 content::BrowserContext*
 NotifierStateTrackerFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextOwnInstanceInIncognito(context);
 }