Today's Nightly States of Flash and HWA are irrelevant STR: Load www.imdb.com and select any video from the three items offered. A panel opens up with the videoplayer, playlist etc. Wait until the video starts. Move the mouse from the panelarea and to the gray semi-transparent area and back, causing mouseover-highlight-effects. ER: The video should continuing to play normally. AR: The video is considerably choppy, the highlight-animation is jerky as well. Regression-range: Last good revision: e1d55bbd1d1d (2010-08-27) First bad revision: 6e3f6d18c124 (2010-08-28) Pushlog: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=e1d55bbd1d1d&tochange=6e3f6d18c124

I can confirm the regression range in comment#0. However, I cannot notice the lag in Firefox10,11,12 release build. Second noticeable regression: Since Firefox13.0. Regression window(m-c) Good: http://hg.mozilla.org/mozilla-central/rev/49afabda6701 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0a1) Gecko/20120115 Firefox/12.0a1 ID:20120115033312 Bad: http://hg.mozilla.org/mozilla-central/rev/823072af2430 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0a1) Gecko/20120115 Firefox/12.0a1 ID:20120115035713 Pushlog: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=49afabda6701&tochange=823072af2430 Regression window(m-i) Good: http://hg.mozilla.org/integration/mozilla-inbound/rev/59cb54c6dfe1 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0a1) Gecko/20120114 Firefox/12.0a1 ID:20120114195007 Bad: http://hg.mozilla.org/integration/mozilla-inbound/rev/5e6e63f3aed8 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0a1) Gecko/20120114 Firefox/12.0a1 ID:20120114201408 Pushlog: http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=59cb54c6dfe1&tochange=5e6e63f3aed8 Suspected : Bug 598482 - Hook up invalidation flushing to the refresh driver and make all painting asynchronous (Bug 598482 was backed out from 12.0, but not 13.0)

Async video and OMTC will fix this.