This allows to use RtcpTransceiver implementation instead of RtpRtcp. No functional changes. Bug: webrtc:8239 Change-Id: I3c5bd23ff2136eb844e85b567b70380fc2a65929 Reviewed-on: https://webrtc-review.googlesource.com/33005 Reviewed-by: Niels Moller <nisse@webrtc.org> Reviewed-by: Philip Eliasson <philipel@webrtc.org> Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/master@{#21298}