Move Singleton and related structs to namespace base

chrome/browser/undo/bookmark_undo_service_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 "chrome/browser/undo/bookmark_undo_service_factory.h"
 
 #include "chrome/browser/profiles/profile.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 #include "components/undo/bookmark_undo_service.h"
 
 // static
 BookmarkUndoService* BookmarkUndoServiceFactory::GetForProfile(
     Profile* profile) {
   return static_cast<BookmarkUndoService*>(
       GetInstance()->GetServiceForBrowserContext(profile, true));
 }
 
 // static
 BookmarkUndoService* BookmarkUndoServiceFactory::GetForProfileIfExists(
     Profile* profile) {
   return static_cast<BookmarkUndoService*>(
       GetInstance()->GetServiceForBrowserContext(profile, false));
 }
 
 // static
 BookmarkUndoServiceFactory* BookmarkUndoServiceFactory::GetInstance() {
-  return Singleton<BookmarkUndoServiceFactory>::get();
+  return base::Singleton<BookmarkUndoServiceFactory>::get();
 }
 
 BookmarkUndoServiceFactory::BookmarkUndoServiceFactory()
     : BrowserContextKeyedServiceFactory(
         "BookmarkUndoService",
         BrowserContextDependencyManager::GetInstance()) {
 }
 
 BookmarkUndoServiceFactory::~BookmarkUndoServiceFactory() {
 }
 
 KeyedService* BookmarkUndoServiceFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
   return new BookmarkUndoService;
 }