This ensures that the MediaChannel interface is only implemented
through a send/receive shim, splitting channels also when kBoth is
used.
Bug: webrtc:13931
Change-Id: Ie97809597eaae7b4f504939339795432c34e56cb
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/307461
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#40210}