Move Singleton and related structs to namespace base

ios/chrome/browser/bookmarks/bookmark_model_factory.cc

 // Copyright 2015 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 "ios/chrome/browser/bookmarks/bookmark_model_factory.h"
 
 #include "base/memory/singleton.h"
 #include "base/prefs/pref_service.h"
 #include "components/bookmarks/browser/bookmark_model.h"
 #include "components/bookmarks/browser/bookmark_utils.h"
@@ skipping 21 matching lines @@
 
 // static
 bookmarks::BookmarkModel* BookmarkModelFactory::GetForBrowserStateIfExists(
     ios::ChromeBrowserState* browser_state) {
   return static_cast<bookmarks::BookmarkModel*>(
       GetInstance()->GetServiceForBrowserState(browser_state, false));
 }
 
 // static
 BookmarkModelFactory* BookmarkModelFactory::GetInstance() {
-  return Singleton<BookmarkModelFactory>::get();
+  return base::Singleton<BookmarkModelFactory>::get();
 }
 
 BookmarkModelFactory::BookmarkModelFactory()
     : BrowserStateKeyedServiceFactory(
           "BookmarkModel",
           BrowserStateDependencyManager::GetInstance()) {
   DependsOn(BookmarkClientFactory::GetInstance());
   DependsOn(ios::BookmarkUndoServiceFactory::GetInstance());
   DependsOn(ios::StartupTaskRunnerServiceFactory::GetInstance());
 }
@@ skipping 29 matching lines @@
 web::BrowserState* BookmarkModelFactory::GetBrowserStateToUse(
     web::BrowserState* context) const {
   return GetBrowserStateRedirectedInIncognito(context);
 }
 
 bool BookmarkModelFactory::ServiceIsNULLWhileTesting() const {
   return true;
 }
 
 }  // namespace ios