Sets aria attributes directly for overflow button.

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

Bug: 836549
Change-Id: Ic122585cacb2c2279f380f844475edc196be451b
Reviewed-on: https://chromium-review.googlesource.com/c/1391909
Commit-Queue: CJ DiMeglio <lethalantidote@chromium.org>
Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: Tommy Steimel <steimel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#633541}
17 files changed