Move Singleton and related structs to namespace base

chrome/browser/bookmarks/managed_bookmark_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 CHROME_BROWSER_BOOKMARKS_MANAGED_BOOKMARK_SERVICE_FACTORY_H_
 #define CHROME_BROWSER_BOOKMARKS_MANAGED_BOOKMARK_SERVICE_FACTORY_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
+namespace base {
 template <typename T>
 struct DefaultSingletonTraits;
+}  // namespace base
+
 class Profile;
 
 namespace bookmarks {
 class ManagedBookmarkService;
 }
 
 // Singleton that owns all ManagedBookmarkServices and associates them with
 // Profile.
 class ManagedBookmarkServiceFactory : public BrowserContextKeyedServiceFactory {
  public:
   static bookmarks::ManagedBookmarkService* GetForProfile(Profile* profile);
   static ManagedBookmarkServiceFactory* GetInstance();
   static TestingFactoryFunction GetDefaultFactory();
 
  private:
-  friend struct DefaultSingletonTraits<ManagedBookmarkServiceFactory>;
+  friend struct base::DefaultSingletonTraits<ManagedBookmarkServiceFactory>;
 
   ManagedBookmarkServiceFactory();
   ~ManagedBookmarkServiceFactory() override;
 
   // BrowserStateKeyedServiceFactory implementation.
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
   content::BrowserContext* GetBrowserContextToUse(
       content::BrowserContext* context) const override;
   bool ServiceIsNULLWhileTesting() const override;
 
   DISALLOW_COPY_AND_ASSIGN(ManagedBookmarkServiceFactory);
 };
 
 #endif  // CHROME_BROWSER_BOOKMARKS_MANAGED_BOOKMARK_SERVICE_FACTORY_H_