Move Singleton and related structs to namespace base

chrome/browser/task_management/providers/web_contents/web_contents_tags_manager.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 "chrome/browser/task_management/providers/web_contents/web_contents_tags_manager.h"
 
 #include "base/memory/singleton.h"
 #include "chrome/browser/task_management/providers/web_contents/web_contents_task_provider.h"
 
 namespace task_management {
 
 // static
 WebContentsTagsManager* WebContentsTagsManager::GetInstance() {
-  return Singleton<WebContentsTagsManager>::get();
+  return base::Singleton<WebContentsTagsManager>::get();
 }
 
 void WebContentsTagsManager::AddTag(WebContentsTag* tag) {
   DCHECK(tag);
   tracked_tags_.push_back(tag);
 
   if (provider_)
     provider_->OnWebContentsTagCreated(tag);
 }
 
@@ skipping 30 matching lines @@
 }
 
 WebContentsTagsManager::WebContentsTagsManager()
     : provider_(nullptr) {
 }
 
 WebContentsTagsManager::~WebContentsTagsManager() {
 }
 
 }  // namespace task_management