Fix paint invalidation when composited layers change from paints-into-ancestor to self-painting.

LayoutTests/fast/repaint/filter-invalidation-with-composited-container-change-expected.txt

 {
   "bounds": [800, 600],
   "children": [
     {
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "repaintRects": [
+        [8, 8, 328, 328],
         [8, 8, 328, 328]
       ],
       "children": [
         {
           "position": [-20, -20],
           "bounds": [256, 256],
           "drawsContent": true,
           "backgroundColor": "#008000",
           "repaintRects": [
             [0, 0, 256, 256],
             [0, 0, 256, 256]
           ]
         }
       ]
     }
   ]
 }