Move Singleton and related structs to namespace base

chrome/browser/signin/chrome_signin_client_factory.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_CHROME_SIGNIN_CLIENT_FACTORY_H_
 #define CHROME_BROWSER_SIGNIN_CHROME_SIGNIN_CLIENT_FACTORY_H_
 
 #include "base/memory/singleton.h"
 #include "chrome/browser/signin/chrome_signin_client.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class Profile;
 
 // Singleton that owns all ChromeSigninClients and associates them with
 // Profiles.
 class ChromeSigninClientFactory : public BrowserContextKeyedServiceFactory {
  public:
   // Returns the instance of SigninClient 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 SigninClient* GetForProfile(Profile* profile);
 
   // Returns an instance of the factory singleton.
   static ChromeSigninClientFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<ChromeSigninClientFactory>;
+  friend struct base::DefaultSingletonTraits<ChromeSigninClientFactory>;
 
   ChromeSigninClientFactory();
   ~ChromeSigninClientFactory() override;
 
   // BrowserContextKeyedServiceFactory:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* profile) const override;
 };
 
 #endif  // CHROME_BROWSER_SIGNIN_CHROME_SIGNIN_CLIENT_FACTORY_H_