Comment 10 for bug 635026

Still, if you use page up and page down aggressively, it'll randomly not trim the pages. But I suspect this has nothing to do with this specific bug, unless it's applying settings in a delayed way. You can cause trimming then by zooming in and out randomly. I don't know what triggers it, but it doesn't bother me as it trims them during autoscroll which is what I need this trimming feature for.