Remove remoting.ClientPlugin interface

remoting/remoting.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
 
     'variables': {
       'conditions': [
@@ skipping 127 matching lines @@
       'webapp/open_sans.css',
       'webapp/open_sans.woff',
       'webapp/scale-to-fit.webp',
       'webapp/spinner.gif',
       'webapp/toolbar.css',
       'webapp/wcs_sandbox.html',
     ],
     'remoting_webapp_js_files': [
       'webapp/butter_bar.js',
       'webapp/client_plugin.js',
-      'webapp/client_plugin_async.js',
       'webapp/client_screen.js',
       'webapp/client_session.js',
       'webapp/clipboard.js',
       'webapp/connection_history.js',
       'webapp/connection_stats.js',
       'webapp/cs_oauth2_trampoline.js',
       'webapp/cs_third_party_auth_trampoline.js',
       'webapp/error.js',
       'webapp/event_handlers.js',
       'webapp/format_iq.js',
@@ skipping 2746 matching lines @@
                   '../base/allocator/allocator.gyp:allocator',
                 ],
               },
             ],
           ],
         }],  # end of 'toolkit_uses_gtk == 1'
       ],  # end of 'conditions'
     },  # end of target 'remoting_unittests'
   ],  # end of targets
 }