STR: 1) Open http://www.thestar.com/news/city_hall/toronto2014election/2014/09/12/ford_brothers_odd_situation_means_they_face_thicket_of_electionfinance_rules.html 2) Make sure the window is big enough to fit the entire page. 3) Scroll down to put the first picture out of the view. 4) Hit APPLE+(plus) twice. The page should go white.

I can reproduce on 64-bit Linux Nightly. (though not in a profile where I have NoScript installed & active; hence, presumably it depends on some set-up-with-script part of the page.)

I can reproduce the problem since Firefox 19 on Windopws7. Regression window(release build) Good: http://hg.mozilla.org/releases/mozilla-release/rev/c4fe2b219941 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:18.0) Gecko/20100101 Firefox/18.0 ID:20130201065344 Bad: http://hg.mozilla.org/releases/mozilla-release/rev/6ffe3e9da8a8 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:19.0) Gecko/20100101 Firefox/19.0 ID:20130307023931 Regression window(m-c) Good: http://hg.mozilla.org/mozilla-central/rev/c29b842c4159 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/16.0 Firefox/16.0a1 ID:20120606221720 Bad: http://hg.mozilla.org/mozilla-central/rev/3933384d8315 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/16.0 Firefox/16.0a1 ID:20120607023619 Pushlog: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=c29b842c4159&tochange=3933384d8315 Regression window(m-i) Good: http://hg.mozilla.org/integration/mozilla-inbound/rev/f5a441d6929f Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/16.0 Firefox/16.0a1 ID:20120605210720 Bad: http://hg.mozilla.org/integration/mozilla-inbound/rev/df6702c41ddd Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/16.0 Firefox/16.0a1 ID:20120605215419 Pushlog: http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=f5a441d6929f&tochange=df6702c41ddd Regressed by: Bug 157681 - [DHTML]We reflow when we should just move And the Bug 157681 was disabled for Fireofx16,17,18.

A simpler testcase would be useful here. (I suppose there's a small chance this is the same as bug 1200585.)