Google is creating an supernew operating system. That’s built from the zero up to run on all devices as phones and desktop computers.
Known as Fuchsia, it seems to be a completely different project to Android and Chrome OS, but its purpose remains unknown.
There's a basic kernel, Magenta, that targets "modern phones and modern personal computers" and the beginnings of a user interface stack to create apps. OS can already be booted onto the Intel NUC mini-computer and Acer Switch 12 laptop, soon on Raspberry Pi 3!
Fuchsia may be planned as an operating system for internal use by Google. It could be intended to power Internet of Things devices that require a scaled-down core, but the inclusion of a sophisticated UI stack doesn't make sense here.