Right now, with TiledCoreAnimationDrawingArea, we accidentally depend on CA implicit animation to do the fade animation when removing a page overlay; we don't use PageOverlay's fade animation (which should be adjusted to use a CA explicit animation, but that's a bug for another day) on the way out (but we do on the way in!). We should make this consistent and update callers. <rdar://problem/12900058>
Created attachment 184641 [details] patch
http://trac.webkit.org/changeset/140769