PPAPI: Make TrackedCallback more threadsafe

ppapi/ppapi_tests.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.
 
 {
   'targets': [
     {
       'target_name': 'ppapi_tests',
       'type': 'loadable_module',
       'include_dirs': [
@@ skipping 156 matching lines @@
         'proxy/plugin_resource_tracker_unittest.cc',
         'proxy/plugin_var_tracker_unittest.cc',
         'proxy/ppb_var_unittest.cc',
         'proxy/ppp_instance_private_proxy_unittest.cc',
         'proxy/ppp_instance_proxy_unittest.cc',
         'proxy/ppp_messaging_proxy_unittest.cc',
         'proxy/printing_resource_unittest.cc',
         'proxy/raw_var_data_unittest.cc',
         'proxy/serialized_var_unittest.cc',
         'proxy/talk_resource_unittest.cc',
+        'proxy/tracked_callback_unittest.cc',
         'proxy/video_decoder_resource_unittest.cc',
         'proxy/websocket_resource_unittest.cc',
         'shared_impl/media_stream_audio_track_shared_unittest.cc',
         'shared_impl/media_stream_buffer_manager_unittest.cc',
         'shared_impl/media_stream_video_track_shared_unittest.cc',
         'shared_impl/proxy_lock_unittest.cc',
         'shared_impl/resource_tracker_unittest.cc',
         'shared_impl/thread_aware_callback_unittest.cc',
         'shared_impl/time_conversion_unittest.cc',
-        'shared_impl/tracked_callback_unittest.cc',
         'shared_impl/var_tracker_unittest.cc',
       ],
       'conditions': [
         [ 'os_posix == 1 and OS != "mac" and OS != "android" and OS != "ios"', {
           'conditions': [
             [ 'use_allocator!="none"', {
               'dependencies': [
                 '../base/allocator/allocator.gyp:allocator',
               ],
             }],
@@ skipping 415 matching lines @@
       'sources': [
         'examples/compositor/compositor.cc',
         'examples/compositor/spinning_cube.cc',
         'examples/compositor/spinning_cube.h',
       ],
     },
     # Adding a new PPAPI example? Don't forget to update the GN build.
     # See //ppapi/examples/BUILD.gn
   ],
 }