Build Identifier: http://hg.mozilla.org/mozilla-central/rev/1374294a6119 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:11.0a1) Gecko/20111111 Firefox/11.0a1 ID:20111111031514 After entering fullscreen mode of Element FullScreen API, "Exit Full Screen" button should be provided when moving mouse to the top of the window. And Clicking the button should return to normal screen mode. Reproducible: Always Steps to Reproduce: 1 Start Firefox with clean profile 2 Open sample html 3 Click "full" button 4 Move mouse pointer to the top of screen Actual Results: Nothing happen Expected Results: "Exit Full Screen" button should be provided when moving mouse to the top of the window. And Clicking the button should return to normal screen mode.