Issue repaints for RenderLayers that get new composited backings after

LayoutTests/compositing/squashing/squash-above-fixed-1-expected.txt

Index: LayoutTests/compositing/squashing/squash-above-fixed-1-expected.txt
diff --git a/LayoutTests/compositing/squashing/squash-above-fixed-1-expected.txt b/LayoutTests/compositing/squashing/squash-above-fixed-1-expected.txt
index 54c0c5980fb91f57d06644c3f3d935ca3a3d9e86..b78413d2c3273695c67af80f8001efbc0c33470c 100644
--- a/LayoutTests/compositing/squashing/squash-above-fixed-1-expected.txt
+++ b/LayoutTests/compositing/squashing/squash-above-fixed-1-expected.txt
@@ -69,11 +69,19 @@ CASE 2, scrolling y to 80, new layers will be squashed, so things repaint:
               (contentsOpaque 1)
               (drawsContent 1)
               (backgroundColor #00FFFF)
+              (repaint rects
+                (rect 0.00 0.00 200.00 100.00)
+              )
             )
             (GraphicsLayer
               (position 0.00 300.00)
               (bounds 200.00 300.00)
               (drawsContent 1)
+              (repaint rects
+                (rect 0.00 200.00 200.00 100.00)
+                (rect 0.00 100.00 200.00 100.00)
+                (rect 0.00 0.00 200.00 100.00)
+              )
             )
           )
         )
@@ -148,11 +156,19 @@ CASE 4, scrolling y to 170 new layers will be squashed, so things repaint:
               (contentsOpaque 1)
               (drawsContent 1)
               (backgroundColor #00FF00)
+              (repaint rects
+                (rect 0.00 0.00 200.00 100.00)
+              )
             )
             (GraphicsLayer
               (position 0.00 400.00)
               (bounds 200.00 300.00)
               (drawsContent 1)
+              (repaint rects
+                (rect 0.00 200.00 200.00 100.00)
+                (rect 0.00 100.00 200.00 100.00)
+                (rect 0.00 0.00 200.00 100.00)
+              )
             )
           )
         )