User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:19.0) Gecko/19.0 Firefox/19.0
Build ID: 20121026030606
Steps to reproduce:
1. enable paint flashing
2.go to http://ie.microsoft.com/testdrive/Performance/ParticleAcceleration/Default.html
full page invalidation and repaint
confirmed that it is invalidating the whole page. Not sure if it should or not - the whole canvas should invalidate, but apparently that should not show as a paint flash, and any Thebes layer should not be invalidating.
This page has two background divs that are size of the full page (backgradient1, backgradient2), and it alternates them between display:block and display:none (such that only only is visible at a time).
This causes us to re-create the frames, and invalidates.
The gradients are also scarily similar (#BEBEBE vs #BFBFBF). I'm not sure what the point of this is, since you definitely can't see the difference. Maybe just to be annoying?
Anyway, this isn't a bug as content is actually changing. I don't see any easy ways to optimize this, and I doubt it's worth the effort.