Move Singleton and related structs to namespace base

chrome/browser/signin/account_fetcher_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_SIGNIN_ACCOUNT_FETCHER_SERVICE_FACTORY_H_
 #define CHROME_BROWSER_SIGNIN_ACCOUNT_FETCHER_SERVICE_FACTORY_H_
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class AccountFetcherService;
 class Profile;
 
 class AccountFetcherServiceFactory : public BrowserContextKeyedServiceFactory {
  public:
   static AccountFetcherService* GetForProfile(Profile* profile);
   static AccountFetcherServiceFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<AccountFetcherServiceFactory>;
+  friend struct base::DefaultSingletonTraits<AccountFetcherServiceFactory>;
 
   AccountFetcherServiceFactory();
   ~AccountFetcherServiceFactory() override;
 
   // BrowserContextKeyedServiceFactory implementation
   void RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) override;
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
 
   DISALLOW_COPY_AND_ASSIGN(AccountFetcherServiceFactory);
 };
 
 #endif  // CHROME_BROWSER_SIGNIN_ACCOUNT_FETCHER_SERVICE_FACTORY_H_