We have to clear the image if there’s area that won’t be painted by the FrameView. <rdar://problem/13375785>
Created attachment 192143 [details] patch
Wait, the coordinates are mixed up.
Maybe we should just unconditionally clear the image — FrameView has the ability to have a non-opaque background, which would still be broken with the “if there’s area that won’t be painted by the FrameView” approach.
I think always clearing the image is fine.
Created attachment 192145 [details] patch
http://trac.webkit.org/changeset/145341