along the lines of RTX handling but with limited support for missing
fmtp lines because of video/red.
BUG=webrtc:13178
Change-Id: Ia866c0e857da6da2ef1e4b81b51f90f534c7bb83
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/231948
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35107}