Adds aria attributes directly to play button

This CL changes the play button to use by aria attributes instead of
explicitly creating accessibility nodes.

Bug: 836549
Change-Id: I08d2b5fd59424388d93ec485a4e3fd7fa7e98e9e
Reviewed-on: https://chromium-review.googlesource.com/c/1394714
Commit-Queue: CJ DiMeglio <lethalantidote@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621933}
6 files changed