[PPAPI] Pepper MediaStream API audio track implementation and example.

ppapi/proxy/media_stream_video_track_resource.cc

Index: ppapi/proxy/media_stream_video_track_resource.cc
diff --git a/ppapi/proxy/media_stream_video_track_resource.cc b/ppapi/proxy/media_stream_video_track_resource.cc
index e8ab4c577251a44e0e3c54dbede7f2eb2dbe83b3..804df00d88f5d90b423f69cde2407190b338d93a 100644
--- a/ppapi/proxy/media_stream_video_track_resource.cc
+++ b/ppapi/proxy/media_stream_video_track_resource.cc
@@ -107,20 +107,24 @@ void MediaStreamVideoTrackResource::Close() {
 }
 
 void MediaStreamVideoTrackResource::OnNewFrameEnqueued() {
-  if (TrackedCallback::IsPending(get_frame_callback_)) {
-    *get_frame_output_ = GetVideoFrame();
-    get_frame_output_ = NULL;
-    scoped_refptr<TrackedCallback> callback;
-    callback.swap(get_frame_callback_);
-    callback->Run(PP_OK);
-  }
+  if (!TrackedCallback::IsPending(get_frame_callback_))
+    return;
+
+  *get_frame_output_ = GetVideoFrame();
+  int32_t result = *get_frame_output_ ? PP_OK : PP_ERROR_FAILED;
+  get_frame_output_ = NULL;
+  scoped_refptr<TrackedCallback> callback;
+  callback.swap(get_frame_callback_);
+  callback->Run(result);
 }
 
 PP_Resource MediaStreamVideoTrackResource::GetVideoFrame() {
   int32_t index = frame_buffer()->DequeueFrame();
   if (index < 0)
     return 0;
+
   MediaStreamFrame* frame = frame_buffer()->GetFramePointer(index);
+  DCHECK(frame);
   scoped_refptr<VideoFrameResource> resource =
       new VideoFrameResource(pp_instance(), index, frame);
   // Add |pp_resource()| and |resource| into |frames_|.