Move Singleton and related structs to namespace base

chrome/browser/media/protected_media_identifier_permission_context_factory.h

 // Copyright 2013 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_MEDIA_PROTECTED_MEDIA_IDENTIFIER_PERMISSION_CONTEXT_FACTORY_H_
 #define CHROME_BROWSER_MEDIA_PROTECTED_MEDIA_IDENTIFIER_PERMISSION_CONTEXT_FACTORY_H_
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class ProtectedMediaIdentifierPermissionContext;
 class Profile;
 
 class ProtectedMediaIdentifierPermissionContextFactory
     : public BrowserContextKeyedServiceFactory {
  public:
   static ProtectedMediaIdentifierPermissionContext* GetForProfile(
       Profile* profile);
 
   static ProtectedMediaIdentifierPermissionContextFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<
+  friend struct base::DefaultSingletonTraits<
       ProtectedMediaIdentifierPermissionContextFactory>;
 
   ProtectedMediaIdentifierPermissionContextFactory();
   ~ProtectedMediaIdentifierPermissionContextFactory() override;
 
   // BrowserContextKeyedBaseFactory methods:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* profile) const override;
   void RegisterProfilePrefs(
       user_prefs::PrefRegistrySyncable* registry) override;
   content::BrowserContext* GetBrowserContextToUse(
       content::BrowserContext* context) const override;
 
   DISALLOW_COPY_AND_ASSIGN(
       ProtectedMediaIdentifierPermissionContextFactory);
 };
 
 #endif  // CHROME_BROWSER_MEDIA_PROTECTED_MEDIA_IDENTIFIER_PERMISSION_CONTEXT_FACTORY_H_