https://bugs.freedesktop.org/show_bug.cgi?id=44695
--- Comment #1 from Benoit Jacob bjacob@mozilla.com 2012-01-11 10:23:53 PST --- Created attachment 55459 --> https://bugs.freedesktop.org/attachment.cgi?id=55459 capture of the canvas, showing the rendering bug
Notice how the limit of the purple are is slightly oblique... maybe that contains a clue as to what the problem is.