I had asked Google the same thing. The browser will load as the last setting for that device type, unless you are running an app in Kiosk mode, at which point it will run in Full Screen mode without the bars. Public sessions cannot enter into full screen mode whatsoever. Not sure why Google made this decision, but they did.
If you login as a user, make the browser full screen and logout again, it should bring the browser up in full screen.