Move Singleton and related structs to namespace base

chrome/browser/signin/signin_error_controller_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_SIGNIN_ERROR_CONTROLLER_FACTORY_H_
 #define CHROME_BROWSER_SIGNIN_SIGNIN_ERROR_CONTROLLER_FACTORY_H_
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 #include "components/signin/core/browser/signin_error_controller.h"
 
 class Profile;
 
 // Singleton that owns all SigninErrorControllers and associates them with
 // Profiles.
 class SigninErrorControllerFactory : public BrowserContextKeyedServiceFactory {
  public:
   // Returns the instance of SigninErrorController associated with this profile
   // (creating one if none exists). Returns NULL if this profile cannot have an
   // SigninClient (for example, if |profile| is incognito).
   static SigninErrorController* GetForProfile(Profile* profile);
 
   // Returns an instance of the factory singleton.
   static SigninErrorControllerFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<SigninErrorControllerFactory>;
+  friend struct base::DefaultSingletonTraits<SigninErrorControllerFactory>;
 
   SigninErrorControllerFactory();
   ~SigninErrorControllerFactory() override;
 
   // BrowserContextKeyedServiceFactory:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* profile) const override;
 };
 
 #endif  // CHROME_BROWSER_SIGNIN_SIGNIN_ERROR_CONTROLLER_FACTORY_H_