Explicitly request key frame on all layers until proper mapping is implemented (webrtc:10615). Bug: webrtc:10585 Change-Id: I9722610920a753c50700d925ff6a1babf0011e2f Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/136682 Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org> Commit-Queue: Sergey Silkin <ssilkin@webrtc.org> Cr-Commit-Position: refs/heads/master@{#27934}