ChromeOS system menu

Coincidently to the release of the Chromebook Plus, we have released a big polish update to our ChromeOS system UI which includes the shelf and the system menu/status tray.

For the shelf, we brought Material Design ripples, icons spacing has been tweaked and we've introduced new activity indicators as well as a new launcher icon. But the biggest chunk of work has been done for the deep refresh and code overhaul of the system menu (holding core system settings) to deliver a cleaner, simpler and pixel perfect UI.

With the release in version 56, we've also brought a new panel, Stylus, which enables quick management of core stylus features, a newly supported input on the ChromeOS platform.