Fix RenderObject::repaintRectangle in situations when the render object is not a layer and is squas…

LayoutTests/compositing/squashing/repaint-squashed-layer-in-rect-expected.txt

 (GraphicsLayer
-  (bounds 800.00 600.00)
+  (bounds 808.00 816.00)
   (children 1
     (GraphicsLayer
-      (bounds 800.00 600.00)
+      (bounds 808.00 816.00)
       (contentsOpaque 1)
       (drawsContent 1)
       (children 1
         (GraphicsLayer
           (children 2
             (GraphicsLayer
               (position 8.00 8.00)
-              (bounds 200.00 200.00)
+              (bounds 800.00 800.00)
               (contentsOpaque 1)
               (drawsContent 1)
-              (backgroundColor #ADD8E6)
+              (backgroundColor #D3D3D3)
             )
             (GraphicsLayer
-              (position 50.00 50.00)
-              (bounds 50.00 50.00)
+              (position 8.00 0.00)
+              (bounds 592.00 600.00)
               (drawsContent 1)
               (repaint rects
-                (rect 0.00 0.00 40.00 40.00)
-                (rect 0.00 0.00 50.00 50.00)
+                (rect 392.00 400.00 200.00 200.00)
+                (rect 392.00 400.00 200.00 200.00)
+                (rect 392.00 400.00 200.00 200.00)
               )
             )
           )
         )
       )
     )
   )
 )