Move Singleton and related structs to namespace base

ios/chrome/browser/signin/signin_client_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_client_factory.h"
 
 #include "base/memory/singleton.h"
 #include "components/keyed_service/core/service_access_type.h"
 #include "components/keyed_service/ios/browser_state_dependency_manager.h"
 #include "ios/chrome/browser/signin/signin_client_impl.h"
 #include "ios/chrome/browser/signin/signin_error_controller_factory.h"
 #include "ios/public/provider/chrome/browser/browser_state/chrome_browser_state.h"
 
 // static
 SigninClient* SigninClientFactory::GetForBrowserState(
     ios::ChromeBrowserState* browser_state) {
   return static_cast<SigninClient*>(
       GetInstance()->GetServiceForBrowserState(browser_state, true));
 }
 
 // static
 SigninClientFactory* SigninClientFactory::GetInstance() {
-  return Singleton<SigninClientFactory>::get();
+  return base::Singleton<SigninClientFactory>::get();
 }
 
 SigninClientFactory::SigninClientFactory()
     : BrowserStateKeyedServiceFactory(
           "SigninClient",
           BrowserStateDependencyManager::GetInstance()) {
   DependsOn(ios::SigninErrorControllerFactory::GetInstance());
 }
 
 SigninClientFactory::~SigninClientFactory() {}
 
 scoped_ptr<KeyedService> SigninClientFactory::BuildServiceInstanceFor(
     web::BrowserState* context) const {
   ios::ChromeBrowserState* chrome_browser_state =
       ios::ChromeBrowserState::FromBrowserState(context);
   return make_scoped_ptr(new SigninClientImpl(
       chrome_browser_state,
       ios::SigninErrorControllerFactory::GetForBrowserState(
           chrome_browser_state)));
 }