There's supposed to be a shadow layer behind the RenderView layer, but we currently hide it. We should transform it along with the RenderView layer, instead.
I did this in https://bugs.webkit.org/show_bug.cgi?id=125750 because it didn't make too much sense to do it once and then reimplement it in the animated way. *** This bug has been marked as a duplicate of bug 125750 ***