Installable applications for Chrome landed in Chrome Dev and Chromium earlier today, and have made it now is possible to expose the new Panels UI as well as a different style of Window built into Chrome. These new UI features give large hints towards how the ChromeOS UI may appear.
Here are the 2 new modes for viewing a webpage (in the new App mode). Notice how both the Panel and the new Window don't show the URL bar. Also, in the new window option, the tab is shown, but if you attempt to open a new tab in this window, it will open in the old window, not within the new App. I'm using a Flash chess game as the example below.
New Panel UI:
New Window UI:
Boring old "I-opened-this-like-any-other-link" UI:
If you have any ideas about how these will fit into ChromeOS (particularily the new window, as we've seen panels demoed as part of ChromeOS already), lets hear about it in the comments section!