GitLab

When a background tile is selected apply the proper border and check
mark. Then remove this stlying when the tile is de-selected.

Bug: 850675
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: Ib1b05121bc6beaae5af6591e3963d59584a1f2af
Reviewed-on: https://chromium-review.googlesource.com/1110352Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Kyle Milka <kmilka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569622}