GitLab

Add selection styling for the shortcut options in the richer picker.

Screenshots:
https://screenshot.googleplex.com/Xhq71uw82du.png
https://screenshot.googleplex.com/EMCRoFfhnrf.png

Bug: 953822
Change-Id: I5c66cd678d99f6a4e47076705c0f59e73424c212
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1638124
Commit-Queue: Kristi Park <kristipark@chromium.org>
Reviewed-by: Kyle Milka <kmilka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665266}