GitLab

This regressed in r255617.

Also add a comment in the CSS file about it being used in other files,
as the dependency is not obvious.

BUG=358523

Review URL: https://codereview.chromium.org/220593006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@268801 0039d316-1c4b-4281-b951-d872f2087c98