GitLab

This adds TalkBack strings to widgets for:
Play/Pause, Mute/Unmute, and elapsed/total time.

Bug: 895776, 656015
Change-Id: I0c815d8afa2452761d743975574156aef40e7441
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2080368
Commit-Queue: Finnur Thorarinsson <finnur@chromium.org>
Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747222}