Move Singleton and related structs to namespace base

ios/chrome/browser/web_data_service_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/web_data_service_factory.h"
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/memory/singleton.h"
@@ skipping 63 matching lines @@
 WebDataServiceFactory::GetTokenWebDataForBrowserState(
     ios::ChromeBrowserState* browser_state,
     ServiceAccessType access_type) {
   WebDataServiceWrapper* wrapper =
       GetForBrowserState(browser_state, access_type);
   return wrapper ? wrapper->GetTokenWebData() : nullptr;
 }
 
 // static
 WebDataServiceFactory* WebDataServiceFactory::GetInstance() {
-  return Singleton<WebDataServiceFactory>::get();
+  return base::Singleton<WebDataServiceFactory>::get();
 }
 
 WebDataServiceFactory::WebDataServiceFactory()
     : BrowserStateKeyedServiceFactory(
           "WebDataService",
           BrowserStateDependencyManager::GetInstance()) {
 }
 
 WebDataServiceFactory::~WebDataServiceFactory() {
 }
@@ skipping 12 matching lines @@
 web::BrowserState* WebDataServiceFactory::GetBrowserStateToUse(
     web::BrowserState* context) const {
   return GetBrowserStateRedirectedInIncognito(context);
 }
 
 bool WebDataServiceFactory::ServiceIsNULLWhileTesting() const {
   return true;
 }
 
 }  // namespace ios