This change passes a pointer (non-owning) down to the MediaChannel when set
in the RtpSender / RtpReceiver. This currently is not used to encrypt frames.
Bug: webrtc:9681
Change-Id: I385fa8b948427803cd3f9cef918c31d7754d1b4f
Reviewed-on: https://webrtc-review.googlesource.com/97000
Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Emad Omara <emadomara@webrtc.org>
Commit-Queue: Benjamin Wright <benwright@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24694}