GitLab

This patch is reland of https://codereview.chromium.org/393283003/ with some fixes.
The corresponding Blink work is at https://codereview.chromium.org/400153002/.

BUG=301515

Review URL: https://codereview.chromium.org/399653003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284113 0039d316-1c4b-4281-b951-d872f2087c98