PPAPI: Implement synchronous postMessage

ppapi/ppapi_proxy.gypi

 # 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.
 
 {
   'target_defaults': {
     'variables': {
       'ppapi_proxy_target': 0,
     },
     'target_conditions': [
@@ skipping 74 matching lines @@
           'proxy/interface_proxy.h',
           'proxy/isolated_file_system_private_resource.cc',
           'proxy/isolated_file_system_private_resource.h',
           'proxy/locking_resource_releaser.h',
           'proxy/media_stream_audio_track_resource.cc',
           'proxy/media_stream_audio_track_resource.h',
           'proxy/media_stream_track_resource_base.cc',
           'proxy/media_stream_track_resource_base.h',
           'proxy/media_stream_video_track_resource.cc',
           'proxy/media_stream_video_track_resource.h',
+          'proxy/message_handler.cc',
+          'proxy/message_handler.h',
           'proxy/net_address_resource.cc',
           'proxy/net_address_resource.h',
           'proxy/network_list_resource.cc',
           'proxy/network_list_resource.h',
           'proxy/network_monitor_resource.cc',
           'proxy/network_monitor_resource.h',
           'proxy/network_proxy_resource.cc',
           'proxy/network_proxy_resource.h',
           'proxy/output_protection_resource.cc',
           'proxy/output_protection_resource.h',
@@ skipping 184 matching lines @@
               'proxy/serialized_flash_menu.cc',
               'proxy/talk_resource.cc',
               'proxy/video_capture_resource.cc',
             ],
           }],
         ],
       }],
     ],
   },
 }