Move Singleton and related structs to namespace base

chrome/browser/signin/about_signin_internals_factory.h

 // Copyright (c) 2012 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_ABOUT_SIGNIN_INTERNALS_FACTORY_H_
 #define CHROME_BROWSER_SIGNIN_ABOUT_SIGNIN_INTERNALS_FACTORY_H_
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class AboutSigninInternals;
 class Profile;
 
 // Singleton that owns all AboutSigninInternals and associates them with
 // Profiles.
 class AboutSigninInternalsFactory : public BrowserContextKeyedServiceFactory {
  public:
   // Returns the instance of AboutSigninInternals associated with this profile,
   // creating one if none exists.
   static AboutSigninInternals* GetForProfile(Profile* profile);
 
   // Returns an instance of the AboutSigninInternalsFactory singleton.
   static AboutSigninInternalsFactory* GetInstance();
 
   // Implementation of BrowserContextKeyedServiceFactory.
   void RegisterProfilePrefs(
       user_prefs::PrefRegistrySyncable* registry) override;
 
  private:
-  friend struct DefaultSingletonTraits<AboutSigninInternalsFactory>;
+  friend struct base::DefaultSingletonTraits<AboutSigninInternalsFactory>;
 
   AboutSigninInternalsFactory();
   ~AboutSigninInternalsFactory() override;
 
   // BrowserContextKeyedServiceFactory
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
 };
 
 #endif  // CHROME_BROWSER_SIGNIN_ABOUT_SIGNIN_INTERNALS_FACTORY_H_