Make much of the proxy thread-safe with 1 great big lock.

ppapi/ppapi_shared.gypi

 # Copyright (c) 2011 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': [
     {
       'target_name': 'ppapi_shared',
       'type': '<(component)',
       'dependencies': [
@@ skipping 42 matching lines @@
         'shared_impl/input_event_impl.cc',
         'shared_impl/input_event_impl.h',
         'shared_impl/instance_impl.cc',
         'shared_impl/instance_impl.h',
         'shared_impl/opengles2_impl.cc',
         'shared_impl/opengles2_impl.h',
         'shared_impl/ppapi_preferences.cc',
         'shared_impl/ppapi_preferences.h',
         'shared_impl/ppp_instance_combined.cc',
         'shared_impl/ppp_instance_combined.h',
+        'shared_impl/proxy_lock.cc',
+        'shared_impl/proxy_lock.h',
         'shared_impl/resource.cc',
         'shared_impl/resource.h',
         'shared_impl/resource_tracker.cc',
         'shared_impl/resource_tracker.h',
         'shared_impl/scoped_pp_resource.cc',
         'shared_impl/scoped_pp_resource.h',
         'shared_impl/time_conversion.cc',
         'shared_impl/time_conversion.h',
         'shared_impl/tracker_base.cc',
         'shared_impl/tracker_base.h',
@@ skipping 97 matching lines @@
         'thunk/ppb_video_layer_api.h',
         'thunk/ppb_video_layer_thunk.cc',
         'thunk/ppb_widget_api.h',
         'thunk/ppb_widget_thunk.cc',
         'thunk/ppb_zoom_thunk.cc',
         'thunk/thunk.h',
       ],
     },
   ],
 }