Animating images in the Welcome to Safari 4 animation jitter. This can be seen especially well with the "Welcome To Safari" text, where the letters appear to be bouncing up and down throughout the slow scale down effect.
I have confirmed that the regression was caused by <http://trac.webkit.org/changeset/42987> (for bug 25458).
It may be best just to back this out for now since it's a simple one-line change, unless there is a way to disable this specifically during animations.
The image code doesn't know that an animation is happening, so doing that would be hard.
The real problem here is that you're rounding after a CSS transform has been applied (and the transform is being animated). Is there a way we can round only when we know that we're not inside a CSS transform?
I think the change shoujld be backed for for now.
Created attachment 29914 [details]
Fixed in <http://trac.webkit.org/changeset/43062>.
The original proposal for https://bugs.webkit.org/show_bug.cgi?id=25458 was to wrap it in #ifdef. I will propose a new patch that contains that contains that change.