Don't look now, but Google has officially revealed their intentions to go after Windows and OS X. Chrome OS 19 has arrived for Samsung Series 5 and Acer AC700 Chromebooks running the developer channel, and the changes it brings may shock you. The newAura window manager has landed, bringing with it a number of features that you'd expect from a traditional OS. For starters, thereís the Shelf along the bottom of the screen. Itís set to hide when youíve got a browser window maximized by default, but you can choose to have it always on top or auto-hide, too, just like the Windows taskbar or OS X dock