Move Singleton and related structs to namespace base

chrome/browser/prerender/prerender_link_manager_factory.h

 // Copyright (c) 2012 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_PRERENDER_PRERENDER_LINK_MANAGER_FACTORY_H_
 #define CHROME_BROWSER_PRERENDER_PRERENDER_LINK_MANAGER_FACTORY_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class Profile;
 
 namespace prerender {
 
 class PrerenderLinkManager;
 
 class PrerenderLinkManagerFactory : public BrowserContextKeyedServiceFactory {
  public:
   static PrerenderLinkManager* GetForProfile(Profile* profile);
   static PrerenderLinkManagerFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<PrerenderLinkManagerFactory>;
+  friend struct base::DefaultSingletonTraits<PrerenderLinkManagerFactory>;
 
   PrerenderLinkManagerFactory();
   ~PrerenderLinkManagerFactory() override {}
 
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* profile) const override;
   content::BrowserContext* GetBrowserContextToUse(
       content::BrowserContext* context) const override;
 };
 
 }  // namespace prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_LINK_MANAGER_FACTORY_H_