Move Singleton and related structs to namespace base

ios/chrome/browser/signin/signin_manager_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_SIGNIN_MANAGER_FACTORY_H_
 #define IOS_CHROME_BROWSER_SIGNIN_SIGNIN_MANAGER_FACTORY_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "components/keyed_service/ios/browser_state_keyed_service_factory.h"
 
+namespace base {
 template <typename T>
 struct DefaultSingletonTraits;
+}  // namespace base
 
 class SigninManagerFactoryObserver;
 class SigninManager;
 class PrefRegistrySimple;
 
 namespace ios {
 
 class ChromeBrowserState;
 
 // Singleton that owns all SigninManagers and associates them with browser
@@ skipping 19 matching lines @@
   // Methods to register or remove observers of SigninManager creation/shutdown.
   void AddObserver(SigninManagerFactoryObserver* observer);
   void RemoveObserver(SigninManagerFactoryObserver* observer);
 
   // Notifies observers of |manager|'s creation. Should be called only by test
   // SigninManager subclasses whose construction does not occur in
   // |BuildServiceInstanceFor()|.
   void NotifyObserversOfSigninManagerCreationForTesting(SigninManager* manager);
 
  private:
-  friend struct DefaultSingletonTraits<SigninManagerFactory>;
+  friend struct base::DefaultSingletonTraits<SigninManagerFactory>;
 
   SigninManagerFactory();
   ~SigninManagerFactory() override;
 
   // List of observers. Checks that list is empty on destruction.
   mutable base::ObserverList<SigninManagerFactoryObserver, true> observer_list_;
 
   // BrowserStateKeyedServiceFactory:
   scoped_ptr<KeyedService> BuildServiceInstanceFor(
       web::BrowserState* context) const override;
   void BrowserStateShutdown(web::BrowserState* context) override;
 };
 }
 
 #endif  // IOS_CHROME_BROWSER_SIGNIN_SIGNIN_MANAGER_FACTORY_H_