ChromeOS
From Gentoo Wiki
Not to be confused with wikipedia:Chromium OS.
ChromeOS is an operating system developed almost exclusively by Google in order to be used on the Chromebook hardware line.
ChromeOS is built[1] using Portage[2], Gentoo's package manager, and Gentoo-based chroots[3]. ChromeOS uses the upstart init system.
ChromeOS Flex now allows ChromeOS to be installed on many commodity machines.