Fix RTPPayloadRegistry to correctly restore RTX, if a valid mapping exists.

webrtc/video_receive_stream.h

Index: webrtc/video_receive_stream.h
diff --git a/webrtc/video_receive_stream.h b/webrtc/video_receive_stream.h
index 68751ddab883725060dd26553552c43befaabdf2..275162ca1cfe4e866de816441afa170b96a87a8e 100644
--- a/webrtc/video_receive_stream.h
+++ b/webrtc/video_receive_stream.h
@@ -133,6 +133,11 @@ class VideoReceiveStream : public ReceiveStream {
       typedef std::map<int, Rtx> RtxMap;
       RtxMap rtx;
 
+      // If set to true, the RTX payload type mapping supplied in |rtx| will be
+      // used when restoring RTX packets. Without it, RTX packets will always be
+      // restored to the last non-RTX packet payload type received.
+      bool use_rtx_payload_mapping_on_restore = false;
+
       // RTP header extensions used for the received stream.
       std::vector<RtpExtension> extensions;
     } rtp;