Require negotiation to send transport cc feedback over RTCP.

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 275162ca1cfe4e866de816441afa170b96a87a8e..1ec7725882f4c3685b0116cbdfbaa815f0cb59d6 100644
--- a/webrtc/video_receive_stream.h
+++ b/webrtc/video_receive_stream.h
@@ -113,6 +113,9 @@ class VideoReceiveStream : public ReceiveStream {
       // See draft-alvestrand-rmcat-remb for information.
       bool remb = false;
 
+      // See draft-holmer-rmcat-transport-wide-cc-extensions for details.
+      bool transport_cc_feedback = false;
+
       // See NackConfig for description.
       NackConfig nack;