Will be later used to conditionally enable mixed codec simulcast with a field trial. Bug: webrtc:42220378 Change-Id: I527a488c04cd2b5a9f4ec703504b67943e966ab0 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/361403 Reviewed-by: Danil Chapovalov <danilchap@webrtc.org> Commit-Queue: Florent Castelli <orphis@webrtc.org> Cr-Commit-Position: refs/heads/main@{#42929}