[SquareWheel]

As far as I know it's the latest source. It doesn't have everything from Chrome OS though, for instance plugins and the auto-updater [1]. Browsing the commits I see an update from 8 minutes ago [2].

[1] http://www.chromium.org/chromium-os/chromium-os-faq

[2] http://git.chromium.org/gitweb/?p=chromium.git;a=summary