GitLab

In the process, removed flattenhtml=true to stop inlining
main.css, and serving it from its own URL instead. Similarly for
other <include> flags in main.html.

Bug: 1132403,1152343
Change-Id: I6c367dd5361111124db4d2592fac67582c7db740
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2629108
Auto-Submit: dpapad <dpapad@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843944}