Support dark mode in theme properties

Bug: 850098

Change-Id: Ic1d51dda680bcc6c24fab1c17099a1d558285528
Reviewed-on: https://chromium-review.googlesource.com/c/1313670
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607289}
1 file changed