Plumbing of feedback on request setting

Bug: webrtc:10263
Change-Id: I23c09e680d6381598e4172b76025ff84f33aa4de
Reviewed-on: https://webrtc-review.googlesource.com/c/121422
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Johannes Kron <kron@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26606}
diff --git a/api/rtp_parameters.h b/api/rtp_parameters.h
index 25a21c1..90e4a4c 100644
--- a/api/rtp_parameters.h
+++ b/api/rtp_parameters.h
@@ -295,6 +295,7 @@
   // Header extension for transport sequence number, see url for details:
   // http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions
   static const char kTransportSequenceNumberUri[];
+  static const char kTransportSequenceNumberV2Uri[];
   static const int kTransportSequenceNumberDefaultId;
 
   static const char kPlayoutDelayUri[];