Replace chrome::NOTIFICATION_EXTENSION_WARNING_CHANGED message with observer pattern

chrome/common/chrome_notification_types.h

 // Copyright (c) 2012 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_COMMON_CHROME_NOTIFICATION_TYPES_H_
 #define CHROME_COMMON_CHROME_NOTIFICATION_TYPES_H_
 
 #include "build/build_config.h"
 #include "content/public/browser/notification_types.h"
 
@@ skipping 665 matching lines @@
   // installed extensions. The source is a Profile, and there are no details.
   // NOTE: It's possible that there are extension updates still being
   // installed by the extension service at the time this notification fires.
   NOTIFICATION_EXTENSION_UPDATING_FINISHED,
 
   // The extension updater found an update and will attempt to download and
   // install it. The source is a Profile, and the details are an extension id
   // (const std::string).
   NOTIFICATION_EXTENSION_UPDATE_FOUND,
 
-  // Sent when one or more extensions changed their warning status (like
-  // slowing down Chrome or conflicting with each other).
-  // The source is a Profile.
-  NOTIFICATION_EXTENSION_WARNING_CHANGED,
-
   // An installed app changed notification state (added or removed
   // notifications). The source is a Profile, and the details are a string
   // with the extension id of the app.
   NOTIFICATION_APP_NOTIFICATION_STATE_CHANGED,
 
   // Finished loading app notification manager.
   // The source is AppNotificationManager, and the details are NoDetails.
   NOTIFICATION_APP_NOTIFICATION_MANAGER_LOADED,
 
   // Component Updater -------------------------------------------------------
@@ skipping 565 matching lines @@
   // Currently only Content and Chrome define and use notifications.
   // Custom notifications not belonging to Content and Chrome should start
   // from here.
   NOTIFICATION_CHROME_END,
 };
 
 }  // namespace chrome
 
 
 #endif  // CHROME_COMMON_CHROME_NOTIFICATION_TYPES_H_