UsePadding - signals to GoogCC that padding should be used to fill up to BWE while BWE is ramping up. Bug: webrtc:12707 Change-Id: I7b4922dff3a83da370c50c567050bfa748190b40 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/324160 Reviewed-by: Diep Bui <diepbp@webrtc.org> Commit-Queue: Per Kjellander <perkj@webrtc.org> Cr-Commit-Position: refs/heads/main@{#40979}