GitLab

Allow users to interact with the custom backgrounds UI with
only the keyboard.

Bug: 851173
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ic442995e2a68d147942ad7625ea0e8a202e40137
Reviewed-on: https://chromium-review.googlesource.com/1097576
Commit-Queue: Kyle Milka <kmilka@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567316}