Added Aura notification that relaunch and powerwash is required in case of downgrade.

chrome/chrome_browser_ui.gypi

 # 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.
 
 {
   'variables': {
     'chrome_browser_ui_non_ios_sources': [
       'browser/ui/accelerator_utils.h',
       'browser/ui/android/android_about_app_info.cc',
       'browser/ui/android/android_about_app_info.h',
@@ skipping 2408 matching lines @@
       'browser/ui/ash/session_state_delegate_chromeos.cc',
       'browser/ui/ash/session_state_delegate_chromeos.h',
       'browser/ui/ash/solid_color_user_wallpaper_delegate.cc',
       'browser/ui/ash/solid_color_user_wallpaper_delegate.h',
       'browser/ui/ash/stub_user_accounts_delegate.cc',
       'browser/ui/ash/stub_user_accounts_delegate.h',
       'browser/ui/ash/system_tray_delegate_chromeos.cc',
       'browser/ui/ash/system_tray_delegate_chromeos.h',
       'browser/ui/ash/system_tray_delegate_linux.cc',
       'browser/ui/ash/system_tray_delegate_linux.h',
+      'browser/ui/ash/system_tray_delegate_utils.cc',
+      'browser/ui/ash/system_tray_delegate_utils.h',
       'browser/ui/ash/system_tray_delegate_win.cc',
       'browser/ui/ash/system_tray_delegate_win.h',
       'browser/ui/ash/user_accounts_delegate_chromeos.cc',
       'browser/ui/ash/user_accounts_delegate_chromeos.h',
       'browser/ui/ash/volume_controller_chromeos.cc',
       'browser/ui/ash/volume_controller_chromeos.h',
       'browser/ui/views/touch_uma/touch_uma_ash.cc',
       'browser/ui/window_sizer/window_sizer_ash.cc',
     ],
     # Used when ash is disabled.
@@ skipping 563 matching lines @@
         }],
         ['OS!="android" and OS!="ios"', {
           'dependencies': [
             '../device/bluetooth/bluetooth.gyp:device_bluetooth',
           ],
         }],
       ],
     },
   ],
 }