Apply a prettier background for platforms that don't support shaped windows.

remoting/app_remoting_webapp_files.gypi

 # 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.
 
 {
   'variables': {
     'ar_shared_resource_files': [
       'webapp/app_remoting/html/ar_dialog.css',
+      'webapp/app_remoting/html/ar_main.css',
       'webapp/app_remoting/html/feedback_consent.css',
       'webapp/app_remoting/html/feedback_consent.html',
       'webapp/app_remoting/html/context_menu.css',
       'resources/drag.webp',
       '<@(remoting_webapp_resource_files)',
     ],
 
     # Variables for main.html.
     # These template files are used to construct the webapp html files.
     'ar_main_template':
@@ skipping 54 matching lines @@
     # Files that contain localizable strings.
     'app_remoting_webapp_localizable_files': [
       '<(ar_main_template)',
       '<@(ar_main_template_files)',
       'webapp/app_remoting/html/feedback_consent.html',
       '<@(ar_all_js_files)',
     ],
 
   },  # end of variables
 }