The intent is that this object can be used instead of VideoMediaChannel,
clearing the way for decomposing VideoMediaChannel into send and
receive classes.
This CL uses it for the "both" role of WebRtcVideoEngine::CreateMediaChannel; a later CL will use it for all roles on all engines.
Bug: webrtc:13931
Change-Id: Ibd0ca2c3c45b5e3bfcced8f7e30a1edd63cf7654
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/306720
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#40173}