GitLab

this is the biggest chunk I can pull out vaguely cleanly.  It does contain a
couple of fake calls to keep the compiler happy.
This CL also makes SetUpMetadata a member in order to ease testing in a later CL.

This depends on https://codereview.chromium.org/261843004/.

BUG=108012

Review URL: https://codereview.chromium.org/266333002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270016 0039d316-1c4b-4281-b951-d872f2087c98