This class will be used in upcoming VideoQualiyObserver.
Bug: none
Change-Id: I7d79a6caf3040a3f707ed8700842dea1de81e0a6
Reviewed-on: https://webrtc-review.googlesource.com/77724
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23343}
