Move Singleton and related structs to namespace base

ios/chrome/browser/google/google_url_tracker_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/google/google_url_tracker_factory.h"
 
 #include "base/memory/singleton.h"
 #include "base/prefs/pref_service.h"
 #include "components/google/core/browser/google_pref_names.h"
 #include "components/google/core/browser/google_url_tracker.h"
 #include "components/keyed_service/ios/browser_state_dependency_manager.h"
 #include "ios/chrome/browser/browser_state/browser_state_otr_helper.h"
 #include "ios/chrome/browser/google/google_url_tracker_client_impl.h"
 #include "ios/public/provider/chrome/browser/browser_state/chrome_browser_state.h"
 
 namespace ios {
 
 // static
 GoogleURLTracker* GoogleURLTrackerFactory::GetForBrowserState(
     ios::ChromeBrowserState* browser_state) {
   return static_cast<GoogleURLTracker*>(
       GetInstance()->GetServiceForBrowserState(browser_state, true));
 }
 
 // static
 GoogleURLTrackerFactory* GoogleURLTrackerFactory::GetInstance() {
-  return Singleton<GoogleURLTrackerFactory>::get();
+  return base::Singleton<GoogleURLTrackerFactory>::get();
 }
 
 GoogleURLTrackerFactory::GoogleURLTrackerFactory()
     : BrowserStateKeyedServiceFactory(
           "GoogleURLTracker",
           BrowserStateDependencyManager::GetInstance()) {
 }
 
 GoogleURLTrackerFactory::~GoogleURLTrackerFactory() {
 }
@@ skipping 25 matching lines @@
 bool GoogleURLTrackerFactory::ServiceIsNULLWhileTesting() const {
   return true;
 }
 
 void GoogleURLTrackerFactory::RegisterBrowserStatePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   GoogleURLTracker::RegisterProfilePrefs(registry);
 }
 
 }  // namespace ios