Add UseCounter and UKM for getVideoPlaybackQuality()

We'd like to know how often the API is used and by which sites.

Bug: 1146016
Change-Id: I4cfb1ea83e08ad96e89bf1a34aadaadf55382e8a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2519424


Commit-Queue: Chrome Cunningham <chcunningham@chromium.org>
Commit-Queue: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Matthew Wolenetz <wolenetz@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Matthew Wolenetz <wolenetz@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Auto-Submit: Chrome Cunningham <chcunningham@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824492}