This does not add it in default SDP offer.
Bug: webrtc:10739
Change-Id: I4e73f4497989fc34f3676927921a4dabb5926096
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/169729
Commit-Queue: Minyue Li <minyue@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Johannes Kron <kron@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30707}