Merge 171683 "Makes windows repaint scrollbars when position cha..."

LayoutTests/platform/win/virtual/gpu/compositedscrolling/overflow/updating-scrolling-content-expected.txt

 (GraphicsLayer
   (bounds 800.00 600.00)
   (children 1
     (GraphicsLayer
       (bounds 800.00 600.00)
       (contentsOpaque 1)
       (drawsContent 1)
       (children 1
         (GraphicsLayer
           (position 8.00 8.00)
@@ skipping 18 matching lines @@
               (position 0.00 185.00)
               (bounds 185.00 15.00)
               (drawsContent 1)
             )
             (GraphicsLayer
               (position 185.00 0.00)
               (bounds 15.00 185.00)
               (drawsContent 1)
               (repaint rects
                 (rect 0.00 0.00 15.00 185.00)
-                (rect 0.00 0.00 15.00 185.00)
-                (rect 0.00 0.00 15.00 185.00)
               )
             )
             (GraphicsLayer
               (position 185.00 185.00)
               (bounds 15.00 15.00)
               (drawsContent 1)
             )
           )
         )
       )
     )
   )
 )