Filing on behalf of dglazkov, originally noted on bug 20329 comment 18. "Landing [r47440 to fix bug 20329] introduced a pretty ghastly regression: The focus ring now snakes around overflowing objects in contenteditable areas. Take a look at this for instance on a ToT: http://trac.webkit.org/export/47638/trunk/LayoutTests/editing/pasteboard/styled-element-markup.html Part of the reason this wasn't caught because we don't run pixel tests on build bots."
Consequence of letting boxes have their full height even in quirks mode. All focus ring rects that are added need to clamp themselves to the root line box top and line box bottom.
This is a quirks-mode-only bug basically.
"pretty ghastly regression" is a bit of an exaggeration by the way, given that contenteditable areas with overflow:visible set are pretty rare (as having an outline grow as you type is pretty bad UI to start with), and that the regression doesn't occur in strict mode either. :)
Created attachment 38405 [details] Patch to clamp to lineTop/lineBottom for all outline rects from line boxes.
Fixed in r47643.