this makes the association between opus and red a bit more obvious.
Also it allows access to the opus payload type which might be
used in the fmtp line in a future CL
BUG=webrtc:11640
Change-Id: I04e0648aedf049d103e3c3481c8712dfc9b79538
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/178800
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31868}
1126a186f6