Move Singleton and related structs to namespace base

chrome/browser/extensions/extension_system_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_EXTENSIONS_EXTENSION_SYSTEM_FACTORY_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SYSTEM_FACTORY_H_
 
 #include "base/memory/singleton.h"
 #include "chrome/browser/extensions/extension_system_impl.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 #include "extensions/browser/extension_system_provider.h"
 
 namespace extensions {
 class ExtensionSystem;
 
 // BrowserContextKeyedServiceFactory for ExtensionSystemImpl::Shared.
 // Should not be used except by ExtensionSystem(Factory).
 class ExtensionSystemSharedFactory : public BrowserContextKeyedServiceFactory {
  public:
   static ExtensionSystemImpl::Shared* GetForBrowserContext(
       content::BrowserContext* context);
 
   static ExtensionSystemSharedFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<ExtensionSystemSharedFactory>;
+  friend struct base::DefaultSingletonTraits<ExtensionSystemSharedFactory>;
 
   ExtensionSystemSharedFactory();
   ~ExtensionSystemSharedFactory() override;
 
   // BrowserContextKeyedServiceFactory implementation:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
   content::BrowserContext* GetBrowserContextToUse(
       content::BrowserContext* context) const override;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionSystemSharedFactory);
 };
 
 // BrowserContextKeyedServiceFactory for ExtensionSystemImpl.
 // TODO(yoz): Rename to ExtensionSystemImplFactory.
 class ExtensionSystemFactory : public ExtensionSystemProvider {
  public:
   // ExtensionSystem provider implementation:
   ExtensionSystem* GetForBrowserContext(
       content::BrowserContext* context) override;
 
   static ExtensionSystemFactory* GetInstance();
 
  private:
-  friend struct DefaultSingletonTraits<ExtensionSystemFactory>;
+  friend struct base::DefaultSingletonTraits<ExtensionSystemFactory>;
 
   ExtensionSystemFactory();
   ~ExtensionSystemFactory() override;
 
   // BrowserContextKeyedServiceFactory implementation:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
   content::BrowserContext* GetBrowserContextToUse(
       content::BrowserContext* context) const override;
   bool ServiceIsCreatedWithBrowserContext() const override;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionSystemFactory);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SYSTEM_FACTORY_H_