Move Singleton and related structs to namespace base

extensions/browser/api/networking_config/networking_config_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 EXTENSIONS_BROWSER_API_NETWORKING_CONFIG_NETWORKING_CONFIG_SERVICE_FACTORY_H_
 #define EXTENSIONS_BROWSER_API_NETWORKING_CONFIG_NETWORKING_CONFIG_SERVICE_FACTORY_H_
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 namespace content {
 class BrowserContext;
 }  // namespace content
 
 namespace extensions {
 class NetworkingConfigService;
 
 class NetworkingConfigServiceFactory
     : public BrowserContextKeyedServiceFactory {
  public:
   static NetworkingConfigService* GetForBrowserContext(
       content::BrowserContext* context);
 
   static NetworkingConfigServiceFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<NetworkingConfigServiceFactory>;
+  friend struct base::DefaultSingletonTraits<NetworkingConfigServiceFactory>;
 
   NetworkingConfigServiceFactory();
   ~NetworkingConfigServiceFactory() override;
 
   // BrowserContextKeyedBaseFactory
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
   content::BrowserContext* GetBrowserContextToUse(
       content::BrowserContext* context) const override;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_API_NETWORKING_CONFIG_NETWORKING_CONFIG_SERVICE_FACTORY_H_