Move Singleton and related structs to namespace base

ios/chrome/browser/signin/signin_manager_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/signin/signin_manager_factory.h"
 
 #include "base/memory/singleton.h"
 #include "base/prefs/pref_registry_simple.h"
 #include "base/time/time.h"
 #include "components/keyed_service/ios/browser_state_dependency_manager.h"
@@ skipping 31 matching lines @@
 
 // static
 SigninManager* SigninManagerFactory::GetForBrowserStateIfExists(
     ios::ChromeBrowserState* browser_state) {
   return static_cast<SigninManager*>(
       GetInstance()->GetServiceForBrowserState(browser_state, false));
 }
 
 // static
 SigninManagerFactory* SigninManagerFactory::GetInstance() {
-  return Singleton<SigninManagerFactory>::get();
+  return base::Singleton<SigninManagerFactory>::get();
 }
 
 void SigninManagerFactory::RegisterBrowserStatePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   SigninManagerBase::RegisterProfilePrefs(registry);
 }
 
 // static
 void SigninManagerFactory::RegisterPrefs(PrefRegistrySimple* registry) {
   SigninManagerBase::RegisterPrefs(registry);
@@ skipping 34 matching lines @@
 void SigninManagerFactory::BrowserStateShutdown(web::BrowserState* context) {
   SigninManager* manager =
       static_cast<SigninManager*>(GetServiceForBrowserState(context, false));
   if (manager)
     FOR_EACH_OBSERVER(SigninManagerFactoryObserver, observer_list_,
                       SigninManagerShutdown(manager));
   BrowserStateKeyedServiceFactory::BrowserStateShutdown(context);
 }
 
 }  // namespace ios