Move Singleton and related structs to namespace base

chrome/browser/signin/signin_error_notifier_factory_ash.h

 // Copyright 2014 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_NOTIFIER_FACTORY_ASH_H_
 #define CHROME_BROWSER_SIGNIN_SIGNIN_ERROR_NOTIFIER_FACTORY_ASH_H_
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class SigninErrorNotifier;
 class Profile;
 
 // Singleton that owns all SigninErrorNotifiers and associates them with
 // Profiles. Listens for the Profile's destruction notification and cleans up
 // the associated SigninErrorNotifier.
 class SigninErrorNotifierFactory : public BrowserContextKeyedServiceFactory {
  public:
   // Returns the instance of SigninErrorNotifier associated with this
   // profile, creating one if none exists and the shell exists.
   static SigninErrorNotifier* GetForProfile(Profile* profile);
 
   // Returns an instance of the SigninErrorNotifierFactory singleton.
   static SigninErrorNotifierFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<SigninErrorNotifierFactory>;
+  friend struct base::DefaultSingletonTraits<SigninErrorNotifierFactory>;
 
   SigninErrorNotifierFactory();
   ~SigninErrorNotifierFactory() override;
 
   // BrowserContextKeyedServiceFactory:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* profile) const override;
 
   DISALLOW_COPY_AND_ASSIGN(SigninErrorNotifierFactory);
 };
 
 #endif  // CHROME_BROWSER_SIGNIN_SIGNIN_ERROR_NOTIFIER_FACTORY_ASH_H_