Move Singleton and related structs to namespace base

chrome/browser/task_management/providers/web_contents/web_contents_tags_manager.h

 // 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.
 
 #ifndef CHROME_BROWSER_TASK_MANAGEMENT_PROVIDERS_WEB_CONTENTS_WEB_CONTENTS_TAGS_MANAGER_H_
 #define CHROME_BROWSER_TASK_MANAGEMENT_PROVIDERS_WEB_CONTENTS_WEB_CONTENTS_TAGS_MANAGER_H_
 
 #include <vector>
 
 #include "chrome/browser/task_management/providers/web_contents/web_contents_tag.h"
 
+namespace base {
 template<typename T>
 struct DefaultSingletonTraits;
+}  // namespace base
 
 namespace task_management {
 
 class WebContentsTaskProvider;
 
 // Defines a manager to track the various TaskManager-specific WebContents
 // UserData (task_management::WebContentsTags). This is used by the
 // WebContentsTaskProvider to get all the pre-existing WebContents once
 // WebContentsTaskProvider::StartUpdating() is called.
 class WebContentsTagsManager {
@@ skipping 13 matching lines @@
   // whose destruction does not correspond to the destruction of their
   // WebContents. In this case the provider (if any) must be manually cleared,
   // or else the corresponding task for the |tag| will continue to exist.
   void ClearFromProvider(const WebContentsTag* tag);
 
   const std::vector<WebContentsTag*>& tracked_tags() const {
     return tracked_tags_;
   }
 
  private:
-  friend struct DefaultSingletonTraits<WebContentsTagsManager>;
+  friend struct base::DefaultSingletonTraits<WebContentsTagsManager>;
 
   WebContentsTagsManager();
   ~WebContentsTagsManager();
 
   // The provider that's currently observing the creation of WebContents.
   WebContentsTaskProvider* provider_;
 
   // A set of all the WebContentsTags seen so far.
   std::vector<WebContentsTag*> tracked_tags_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentsTagsManager);
 };
 
 }  // namespace task_management
 
 
 #endif  // CHROME_BROWSER_TASK_MANAGEMENT_PROVIDERS_WEB_CONTENTS_WEB_CONTENTS_TAGS_MANAGER_H_