GitLab

Makes shelf control buttons (home, back, overview) show up regardless of
kHideShelfControlsInTabletMode if they're needed for accessibiltiy
reasons - i.e. if one of the accessibility features is enabled:
*   spoken feedback
*   autoclick
*   switch access

BUG=1012814

Change-Id: I83925d201e8551a694a444a8cbc1f69d71892a7a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2024034
Commit-Queue: Toni Baržić <tbarzic@chromium.org>
Reviewed-by: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735992}