This done in preparation of VP9 support. Bug: webrtc:12354 Change-Id: Iabd220f9c7af2694374be1fc0f0de9a2deda3470 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/201386 Commit-Queue: Erik Språng <sprang@webrtc.org> Reviewed-by: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/master@{#32998}