Comment 58 for bug 109943

Here is a trace while copying emails between folders on an IMAP server. Some work is actually being done, but there seems to be a lot of time spent in
Paint::PresShell::Paint
nsLayoutUtils::PaintFrame
nsDisplayList::PaintRoot

https://people.mozilla.org/~bgirard/cleopatra/?1418817484580#report=f2ec94e59158f41a3723d4d2d517587d1476ab41