[Chromoting] Enable remoting webapp main.html GN build.

remoting/remoting_client.gypi

 # Copyright 2014 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.
 
 {
   'targets': [
     {
       # GN version: //remoting/client/plugin
       'target_name': 'remoting_client_plugin',
       'type': 'static_library',
@@ skipping 31 matching lines @@
         'remoting_protocol',
         '../third_party/libyuv/libyuv.gyp:libyuv',
         '../third_party/webrtc/modules/modules.gyp:desktop_capture',
       ],
       'sources': [
         '<@(remoting_client_sources)',
       ],
     },  # end of target 'remoting_client'
 
     {
+      # Keep in sync with remoting/webapp/BUILD.gn
       'target_name': 'remoting_webapp_html',
       'type': 'none',
       'actions': [
         {
           # GN version: //remoting/webapp:html
           'action_name': 'Build Remoting Webapp main.html',
           'inputs': [
             'webapp/build-html.py',
             '<(remoting_webapp_template_main)',
             '<@(remoting_webapp_template_files)',
@@ skipping 115 matching lines @@
                 ],
               },
             }],
           ],
           'includes': [ 'remoting_webapp.gypi', ],
         },  # end of target 'remoting_webapp_v2'
       ],
     }],
   ],
 }