Changing scrim color when the box is focused

Bug: 934465
Change-Id: I2147c3c8a4a6a68f6f8382b320c1cf61ac8758ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1531726
Reviewed-by: Theresa <twellington@chromium.org>
Reviewed-by: Becky Zhou <huayinz@chromium.org>
Commit-Queue: Sinan Sahin <sinansahin@google.com>
Cr-Commit-Position: refs/heads/master@{#642598}