[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 0b76fb8c45704ab600b4f152c73b9bee9c38c157..da149fc8b0d05e2c8896dc2edd65c1cbffe36755 100644
--- a/ppapi/proxy/media_stream_video_track_resource.cc
+++ b/ppapi/proxy/media_stream_video_track_resource.cc
@@ -54,7 +54,7 @@ int32_t MediaStreamVideoTrackResource::GetFrame(
   if (TrackedCallback::IsPending(get_frame_callback_))
     return PP_ERROR_INPROGRESS;
 
-  *frame = GetVideoFrame();
+  *frame = GetVideoFrame(-1);
   if (*frame)
     return PP_OK;
 
@@ -96,21 +96,26 @@ void MediaStreamVideoTrackResource::Close() {
   MediaStreamTrackResourceBase::CloseInternal();
 }
 
-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);
-  }
+bool MediaStreamVideoTrackResource::OnNewFramePreEnqueued(int32_t index) {
+  if (!TrackedCallback::IsPending(get_frame_callback_))
+    return false;
+
+  *get_frame_output_ = GetVideoFrame(index);
+  get_frame_output_ = NULL;
+  scoped_refptr<TrackedCallback> callback;
+  callback.swap(get_frame_callback_);
+  callback->Run(PP_OK);
+  return true;
 }
 
-PP_Resource MediaStreamVideoTrackResource::GetVideoFrame() {
-  int32_t index = frame_buffer()->DequeueFrame();
-  if (index < 0)
-    return 0;
+PP_Resource MediaStreamVideoTrackResource::GetVideoFrame(int32_t index) {
+  if (index < 0) {
+    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_|.