Source: http://www.engadget.com/2013/11/19/chrome-os-32-beta/
Windowing has been a familiar sight in Chrome OS for a while now, but it hasn't always been easy to find the window you're looking for. That search should be much quicker if you're running the just-launched Chrome OS 32 beta, though. The test release brings Vista-style window thumbnails when using Alt-Tab to switch tasks, and the overview button now shows an organized view of all those panes. Early adopters can get the beta today, although it's not currently available for either the original Acer C7 or the HP Pavilion 14 Chromebook.
Source: Chrome Releases