The extension was added behind the WebRTC-GenericDescriptorAdvertised field trial. Bug: webrtc:9361 Change-Id: I84c2d54405e38fae6361dc326ad72495733584a6 Reviewed-on: https://webrtc-review.googlesource.com/c/104622 Reviewed-by: Rasmus Brandt <brandtr@webrtc.org> Reviewed-by: Erik Språng <sprang@webrtc.org> Commit-Queue: Philip Eliasson <philipel@webrtc.org> Cr-Commit-Position: refs/heads/master@{#25052}