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.cc b/api/rtp_parameters.cc
index c4fd112..6de14da 100644
--- a/api/rtp_parameters.cc
+++ b/api/rtp_parameters.cc
@@ -108,6 +108,8 @@
 
 const char RtpExtension::kTransportSequenceNumberUri[] =
     "http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01";
+const char RtpExtension::kTransportSequenceNumberV2Uri[] =
+    "http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-02";
 const int RtpExtension::kTransportSequenceNumberDefaultId = 5;
 
 // This extension allows applications to adaptively limit the playout delay