Separate repaint and layout requirements of StyleDifference (Step 4)

LayoutTests/fast/repaint/fixed-move-after-scroll-expected.txt

 You should see a yellow rect on the left, and a green one on the right. No red pixels.
 (GraphicsLayer
   (bounds 785.00 3016.00)
   (children 1
     (GraphicsLayer
       (bounds 785.00 3016.00)
       (contentsOpaque 1)
       (drawsContent 1)
       (repaint rects
         (rect 10.00 270.00 100.00 100.00)
-        (rect 10.00 270.00 100.00 100.00)
-        (rect 10.00 270.00 100.00 100.00)
         (rect 150.00 270.00 100.00 100.00)
       )
     )
   )
 )