CSS clip property should not force additional clamping to border box

LayoutTests/compositing/geometry/clip-expected.txt

 Test CSS clip with composited layers. Left and right sides should look the same.
 
 (GraphicsLayer
   (bounds 800.00 600.00)
   (children 1
     (GraphicsLayer
       (bounds 800.00 600.00)
       (contentsOpaque 1)
       (drawsContent 1)
       (children 2
         (GraphicsLayer
-          (position 20.00 20.00)
-          (bounds 100.00 100.00)
-          (contentsOpaque 1)
+          (position 15.00 15.00)
+          (bounds 110.00 110.00)
           (drawsContent 1)
           (backgroundColor #808080)
           (transform [1.00 0.00 0.00 0.00] [0.00 1.00 0.00 0.00] [0.00 0.00 1.00 0.00] [0.00 0.00 1.00 1.00])
         )
         (GraphicsLayer
           (position 215.00 15.00)
           (bounds 110.00 110.00)
           (children 1
             (GraphicsLayer
               (position -5.00 -5.00)
               (bounds 120.00 120.00)
               (drawsContent 1)
               (backgroundColor #00000033)
               (transform [1.00 0.00 0.00 0.00] [0.00 1.00 0.00 0.00] [0.00 0.00 1.00 0.00] [0.00 0.00 1.00 1.00])
             )
           )
         )
       )
     )
   )
 )