Move Singleton and related structs to namespace base

ios/chrome/browser/signin/account_fetcher_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 "ios/chrome/browser/signin/account_fetcher_service_factory.h"
 
 #include "base/memory/singleton.h"
 #include "components/invalidation/impl/profile_invalidation_provider.h"
 #include "components/invalidation/public/invalidation_service.h"
 #include "components/keyed_service/ios/browser_state_dependency_manager.h"
@@ skipping 21 matching lines @@
 
 // static
 AccountFetcherService* AccountFetcherServiceFactory::GetForBrowserState(
     ios::ChromeBrowserState* browser_state) {
   return static_cast<AccountFetcherService*>(
       GetInstance()->GetServiceForBrowserState(browser_state, true));
 }
 
 // static
 AccountFetcherServiceFactory* AccountFetcherServiceFactory::GetInstance() {
-  return Singleton<AccountFetcherServiceFactory>::get();
+  return base::Singleton<AccountFetcherServiceFactory>::get();
 }
 
 void AccountFetcherServiceFactory::RegisterBrowserStatePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   AccountFetcherService::RegisterPrefs(registry);
 }
 
 scoped_ptr<KeyedService> AccountFetcherServiceFactory::BuildServiceInstanceFor(
     web::BrowserState* context) const {
   ios::ChromeBrowserState* browser_state =
       ios::ChromeBrowserState::FromBrowserState(context);
   scoped_ptr<AccountFetcherService> service(new AccountFetcherService());
   invalidation::ProfileInvalidationProvider* invalidation_provider =
       ios::GetKeyedServiceProvider()
           ->GetProfileInvalidationProviderForBrowserState(browser_state);
   invalidation::InvalidationService* invalidation_service =
       invalidation_provider->GetInvalidationService();
   service->Initialize(
       SigninClientFactory::GetForBrowserState(browser_state),
       OAuth2TokenServiceFactory::GetForBrowserState(browser_state),
       ios::AccountTrackerServiceFactory::GetForBrowserState(browser_state),
       invalidation_service);
   return service.Pass();
 }
 
 }  // namespace ios