Move Singleton and related structs to namespace base

ios/chrome/browser/suggestions/suggestions_service_factory.mm

 // Copyright 2014 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/suggestions/suggestions_service_factory.h"
 
 #include "base/files/file_path.h"
 #include "base/memory/singleton.h"
 #include "base/sequenced_task_runner.h"
 #include "base/threading/sequenced_worker_pool.h"
@@ skipping 10 matching lines @@
 #include "ios/web/public/web_thread.h"
 
 namespace suggestions {
 namespace {
 const base::FilePath::CharType kThumbnailDirectory[] =
     FILE_PATH_LITERAL("Thumbnail");
 }
 
 // static
 SuggestionsServiceFactory* SuggestionsServiceFactory::GetInstance() {
-  return Singleton<SuggestionsServiceFactory>::get();
+  return base::Singleton<SuggestionsServiceFactory>::get();
 }
 
 // static
 SuggestionsService* SuggestionsServiceFactory::GetForBrowserState(
     ios::ChromeBrowserState* browser_state) {
   return static_cast<SuggestionsService*>(
       GetInstance()->GetServiceForBrowserState(browser_state, true));
 }
 
 SuggestionsServiceFactory::SuggestionsServiceFactory()
@@ skipping 33 matching lines @@
       browser_state->GetRequestContext(), suggestions_store.Pass(),
       thumbnail_manager.Pass(), blacklist_store.Pass()));
 }
 
 void SuggestionsServiceFactory::RegisterBrowserStatePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   SuggestionsService::RegisterProfilePrefs(registry);
 }
 
 }  // namespace suggestions