Move Singleton and related structs to namespace base

ios/chrome/browser/signin/gaia_cookie_manager_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 IOS_CHROME_BROWSER_SIGNIN_GAIA_COOKIE_MANAGER_SERVICE_FACTORY_H_
 #define IOS_CHROME_BROWSER_SIGNIN_GAIA_COOKIE_MANAGER_SERVICE_FACTORY_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "components/keyed_service/ios/browser_state_keyed_service_factory.h"
 
 template <typename T>
-struct DefaultSingletonTraits;
+struct base::DefaultSingletonTraits;
 class GaiaCookieManagerService;
 
 namespace ios {
 
 class ChromeBrowserState;
 
 // Singleton that owns the GaiaCookieManagerService(s) and associates them with
 // browser states.
 class GaiaCookieManagerServiceFactory : public BrowserStateKeyedServiceFactory {
  public:
   // Returns the instance of GaiaCookieManagerService associated with this
   // browser state (creating one if none exists). Returns null if this browser
   // state cannot have an GaiaCookieManagerService (for example, if it is
   // incognito).
   static GaiaCookieManagerService* GetForBrowserState(
       ios::ChromeBrowserState* browser_state);
 
   // Returns an instance of the factory singleton.
   static GaiaCookieManagerServiceFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<GaiaCookieManagerServiceFactory>;
+  friend struct base::DefaultSingletonTraits<GaiaCookieManagerServiceFactory>;
 
   GaiaCookieManagerServiceFactory();
   ~GaiaCookieManagerServiceFactory() override;
 
   // BrowserStateKeyedServiceFactory:
   scoped_ptr<KeyedService> BuildServiceInstanceFor(
       web::BrowserState* context) const override;
 
   DISALLOW_COPY_AND_ASSIGN(GaiaCookieManagerServiceFactory);
 };
 
 }  // namespace ios
 
 #endif  // IOS_CHROME_BROWSER_SIGNIN_GAIA_COOKIE_MANAGER_SERVICE_FACTORY_H_