Move Singleton and related structs to namespace base

extensions/browser/extension_registry_factory.cc

 // 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.
 
 #include "extensions/browser/extension_registry_factory.h"
 
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/extensions_browser_client.h"
 
 using content::BrowserContext;
 
 namespace extensions {
 
 // static
 ExtensionRegistry* ExtensionRegistryFactory::GetForBrowserContext(
     BrowserContext* context) {
   return static_cast<ExtensionRegistry*>(
       GetInstance()->GetServiceForBrowserContext(context, true));
 }
 
 // static
 ExtensionRegistryFactory* ExtensionRegistryFactory::GetInstance() {
-  return Singleton<ExtensionRegistryFactory>::get();
+  return base::Singleton<ExtensionRegistryFactory>::get();
 }
 
 ExtensionRegistryFactory::ExtensionRegistryFactory()
     : BrowserContextKeyedServiceFactory(
           "ExtensionRegistry",
           BrowserContextDependencyManager::GetInstance()) {
   // No dependencies on other services.
 }
 
 ExtensionRegistryFactory::~ExtensionRegistryFactory() {}
 
 KeyedService* ExtensionRegistryFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
   return new ExtensionRegistry(context);
 }
 
 BrowserContext* ExtensionRegistryFactory::GetBrowserContextToUse(
     BrowserContext* context) const {
   // Redirected in incognito.
   return ExtensionsBrowserClient::Get()->GetOriginalContext(context);
 }
 
 }  // namespace extensions