Start documenting the threading model

webrtc/modules/video_coding/video_receiver.cc

Index: webrtc/modules/video_coding/video_receiver.cc
diff --git a/webrtc/modules/video_coding/video_receiver.cc b/webrtc/modules/video_coding/video_receiver.cc
index 9dc8eaab996388346def18b23c8d09cf9d0234b0..cd5877d24ea3b6d5bb6f86a3e04c2d36ad020772 100644
--- a/webrtc/modules/video_coding/video_receiver.cc
+++ b/webrtc/modules/video_coding/video_receiver.cc
@@ -358,6 +358,11 @@ int32_t VideoReceiver::Decode(const VCMEncodedFrame& frame) {
   return ret;
 }
 
+void VideoReceiver::PollDecodedFrames() {
+  if (_decoder)
+    _decoder->PollDecodedFrames();
+}
+
 // Register possible receive codecs, can be called multiple times
 int32_t VideoReceiver::RegisterReceiveCodec(const VideoCodec* receiveCodec,
                                             int32_t numberOfCores,