Comment 5 for bug 749440

Ok, so what this extension appears to be doing is setting list-image-style to a large image (mosaic.png), and only clips it with -moz-image-region under certain conditions (ie, when it's visible to the user). Having list-image-style=mosaic.png with no -moz-image-region is what breaks it, because it means we set the icon to the whole mosaic.png image, which is a pretty big file.

I think the only thing I can do is just disable icons when they are unusually large. In any case, this extension isn't going to do what you expect for menus with globalmenu-extension (we don't get any hover events from the menu for example)