Adds test for experimental remote estimate SDP negotiation.

Bug: webrtc:10742
Change-Id: I50d9caecda10c504cb4880c37475eeccd22c0855
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/146705
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28670}
diff --git a/modules/rtp_rtcp/source/rtcp_packet/remote_estimate.h b/modules/rtp_rtcp/source/rtcp_packet/remote_estimate.h
index a63b624..ebf7fef 100644
--- a/modules/rtp_rtcp/source/rtcp_packet/remote_estimate.h
+++ b/modules/rtp_rtcp/source/rtcp_packet/remote_estimate.h
@@ -32,6 +32,9 @@
 // overhead of the serializer every time RemoteEstimate is created.
 const RemoteEstimateSerializer* GetRemoteEstimateSerializer();
 
+// The RemoteEstimate packet provides network estimation results from the
+// receive side. This functionality is experimental and subject to change
+// without notice.
 class RemoteEstimate : public App {
  public:
   RemoteEstimate();