Move Singleton and related structs to namespace base

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