Move Singleton and related structs to namespace base

chrome/browser/plugins/plugin_prefs_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_PLUGINS_PLUGIN_PREFS_FACTORY_H_
 #define CHROME_BROWSER_PLUGINS_PLUGIN_PREFS_FACTORY_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/refcounted_browser_context_keyed_service_factory.h"
 
 class PluginPrefs;
 class Profile;
 
 class PluginPrefsFactory : public RefcountedBrowserContextKeyedServiceFactory {
  public:
   static scoped_refptr<PluginPrefs> GetPrefsForProfile(Profile* profile);
 
   static PluginPrefsFactory* GetInstance();
 
  private:
   friend class PluginPrefs;
-  friend struct DefaultSingletonTraits<PluginPrefsFactory>;
+  friend struct base::DefaultSingletonTraits<PluginPrefsFactory>;
 
   // Helper method for PluginPrefs::GetForTestingProfile.
   static scoped_refptr<RefcountedKeyedService> CreateForTestingProfile(
       content::BrowserContext* profile);
 
   PluginPrefsFactory();
   ~PluginPrefsFactory() override;
 
   // RefcountedBrowserContextKeyedServiceFactory methods:
   scoped_refptr<RefcountedKeyedService> BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
 
   // BrowserContextKeyedServiceFactory methods:
   void RegisterProfilePrefs(
       user_prefs::PrefRegistrySyncable* registry) override;
   content::BrowserContext* GetBrowserContextToUse(
       content::BrowserContext* context) const override;
   bool ServiceIsNULLWhileTesting() const override;
   bool ServiceIsCreatedWithBrowserContext() const override;
 };
 
 #endif  // CHROME_BROWSER_PLUGINS_PLUGIN_PREFS_FACTORY_H_