Move Singleton and related structs to namespace base

extensions/browser/warning_service_factory.cc

 // Copyright 2014 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.
 
 #include "extensions/browser/warning_service_factory.h"
 
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 #include "extensions/browser/extension_registry_factory.h"
 #include "extensions/browser/extensions_browser_client.h"
 #include "extensions/browser/warning_service.h"
 
 using content::BrowserContext;
 
 namespace extensions {
 
 // static
 WarningService* WarningServiceFactory::GetForBrowserContext(
     BrowserContext* context) {
   return static_cast<WarningService*>(
       GetInstance()->GetServiceForBrowserContext(context, true));
 }
 
 // static
 WarningServiceFactory* WarningServiceFactory::GetInstance() {
-  return Singleton<WarningServiceFactory>::get();
+  return base::Singleton<WarningServiceFactory>::get();
 }
 
 WarningServiceFactory::WarningServiceFactory()
     : BrowserContextKeyedServiceFactory(
           "WarningService",
           BrowserContextDependencyManager::GetInstance()) {
   DependsOn(ExtensionRegistryFactory::GetInstance());
 }
 
 WarningServiceFactory::~WarningServiceFactory() {
 }
 
 KeyedService* WarningServiceFactory::BuildServiceInstanceFor(
     BrowserContext* context) const {
   return new WarningService(context);
 }
 
 BrowserContext* WarningServiceFactory::GetBrowserContextToUse(
     BrowserContext* context) const {
   // Redirected in incognito.
   return ExtensionsBrowserClient::Get()->GetOriginalContext(context);
 }
 
 }  // namespace extensions