Build Identifier: http://hg.mozilla.org/mozilla-central/rev/c60535115ea1 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:11.0a1) Gecko/20111110 Firefox/11.0a1 ID:20111110031403 Exiting full-screen of Youtube HTML5 video does not return normal mode. Chrome works well. Reproducible: Always Steps to Reproduce: 1 Start Firefox with clean profile 2 Open http://www.youtube.com/watch?v=BRG5VNNUq_E&hd=1&html5=1 3.Click Full screen Icon at the bottom-right corner of the video --- The video become real full-screen. 4.Exit full-screen by ESC key or the Icon. --- Became old style full screen. Actual Results: Exiting full-screen of Youtube HTML5 video does not return normal mode. The video contents fill up the browser.(i.e old style full screen) Expected Results: The video size should return to normal size. Regression window with user_pref("full-screen-api.enabled", true)(m-c), Works: http://hg.mozilla.org/mozilla-central/rev/6e219763ddd0 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:10.0a1) Gecko/20111101 Firefox/10.0a1 ID:20111101052615 Fails: http://hg.mozilla.org/mozilla-central/rev/cd9add22f090 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:10.0a1) Gecko/20111101 Firefox/10.0a1 ID:20111101073309 pushlog: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=6e219763ddd0&tochange=cd9add22f090 Regression window with user_pref("full-screen-api.enabled", true)(m-i), Works: http://hg.mozilla.org/integration/mozilla-inbound/rev/470ed3885e3c Mozilla/5.0 (Windows NT 6.1; WOW64; rv:10.0a1) Gecko/20111031 Firefox/10.0a1 ID:20111031213915 Fails: http://hg.mozilla.org/integration/mozilla-inbound/rev/ad6054dd6e08 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:10.0a1) Gecko/20111031 Firefox/10.0a1 ID:20111031235715 pushlog: http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=470ed3885e3c&tochange=ad6054dd6e08 Suspected: Bug 694204 - ESC to exit DOM full-screen stops all loads in doc

I have verified that this is caused by: b72b2c0f996f Chris Pearce — Bug 685779 - Add -moz-full-screen-ancestor pseudo class. r=bz I bet their "mozfullscreenchange" event listener is only on their full-screen element, and not the the document. We changed to dispatching "mozfullscreenchange" on full-screen exit to the document rather than the element in that changeset. I'll email my contacts at YouTube to see if this is the case.

I have emailed my contacts at YouTube, and a fix should be out in this coming week.

YouTube's fix appears to be live now.