Part of a set of CL to allow video to borrow underused audio bitrate.
Bug: webrtc:35055527
Change-Id: Idb504cbbc5794c06b28bdc21b3d860c9da9df175
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/358202
Reviewed-by: Jakob Ivarsson <jakobi@webrtc.org>
Commit-Queue: Dan Tan <dwtan@google.com>
Cr-Commit-Position: refs/heads/main@{#42733}