GitLab

This CL polishes the interstitial screen including:
 - Makes progress bar the same width as the bubble.
 - Updates constants to spec.
Screenshot: https://screenshot.googleplex.com/73uEHo56GiKENdQ.png

Misc: removes unused |AddSeparator| function.

BUG=1106937,1126208

Change-Id: If44bd19b8347a0385dd0be975fd42189eb4a4a01
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2495977
Commit-Queue: Meilin Wang <meilinw@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Tim Song <tengs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821401}