WebUI Dark Mode: change history separator color based on UX feedback

Screenshot: https://imgur.com/a/FvyORNg

R=hcarmona@chromium.org
BUG=923597

Change-Id: I10e1fc834072a4193db65f04db0d78b2bc56117a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1500598
Commit-Queue: Dan Beam <dbeam@chromium.org>
Commit-Queue: Hector Carmona <hcarmona@chromium.org>
Auto-Submit: Dan Beam <dbeam@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637497}
1 file changed