Move Singleton and related structs to namespace base

apps/app_lifetime_monitor_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 APPS_APP_LIFETIME_MONITOR_FACTORY_H_
 #define APPS_APP_LIFETIME_MONITOR_FACTORY_H_
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class Profile;
 
 namespace apps {
 
 class AppLifetimeMonitor;
 
 // Singleton that owns all AppLifetimeMonitors and associates them with
 // Profiles. Listens for the Profile's destruction notification and cleans up
 // the associated AppLifetimeMonitor.
 class AppLifetimeMonitorFactory : public BrowserContextKeyedServiceFactory {
  public:
   static AppLifetimeMonitor* GetForProfile(Profile* profile);
 
   static AppLifetimeMonitorFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<AppLifetimeMonitorFactory>;
+  friend struct base::DefaultSingletonTraits<AppLifetimeMonitorFactory>;
 
   AppLifetimeMonitorFactory();
   ~AppLifetimeMonitorFactory() override;
 
   // BrowserContextKeyedServiceFactory:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* profile) const override;
   bool ServiceIsCreatedWithBrowserContext() const override;
   content::BrowserContext* GetBrowserContextToUse(
       content::BrowserContext* context) const override;
 };
 
 }  // namespace apps
 
 #endif  // APPS_APP_LIFETIME_MONITOR_FACTORY_H_