Add update available icon in system tray

chrome/browser/chrome_notification_types.h

 // Copyright 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_BROWSER_CHROME_NOTIFICATION_TYPES_H_
 #define CHROME_BROWSER_CHROME_NOTIFICATION_TYPES_H_
 
 #include "build/build_config.h"
 #include "extensions/features/features.h"
 
@@ skipping 255 matching lines @@
   NOTIFICATION_PRINT_JOB_RELEASED,
 
   // Upgrade notifications ---------------------------------------------------
 
   // Sent when Chrome believes an update has been installed and available for
   // long enough with the user shutting down to let it take effect. See
   // upgrade_detector.cc for details on how long it waits. No details are
   // expected.
   NOTIFICATION_UPGRADE_RECOMMENDED,
 
+  // Sent when Chrome believes an update is available, but downloading requires

[sky, 2017/05/18 15:50:43]

Seen comments on line 25-27. What would it take to not use notifications?

[weidongg, 2017/05/18 20:36:35]

Oh, I didn't notice that. I migrate this notification to observer.

+  // user's permission as current connection is cellular.
+  NOTIFICATION_UPDATE_OVER_CELLULAR_AVAILABLE,
+
   // Sent when a critical update has been installed. No details are expected.
   NOTIFICATION_CRITICAL_UPGRADE_INSTALLED,
 
   // Sent when the current install is outdated. No details are expected.
   NOTIFICATION_OUTDATED_INSTALL,
 
   // Sent when the current install is outdated and auto-update (AU) is disabled.
   // No details are expected.
   NOTIFICATION_OUTDATED_INSTALL_NO_AU,
 
@@ skipping 177 matching lines @@
   // Note:-
   // 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_BROWSER_CHROME_NOTIFICATION_TYPES_H_