Issue repaints before and after changing the squashing assignment of a RenderLayer.

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 4cf96541ddf0cdc3ab61cfdc7eac2a85f527940a..54c0c5980fb91f57d06644c3f3d935ca3a3d9e86 100644
--- a/LayoutTests/compositing/squashing/squash-above-fixed-1-expected.txt
+++ b/LayoutTests/compositing/squashing/squash-above-fixed-1-expected.txt
@@ -47,6 +47,9 @@ CASE 2, scrolling y to 80, new layers will be squashed, so things repaint:
       (contentsOpaque 1)
       (drawsContent 1)
       (repaint rects
+        (rect 0.00 500.00 200.00 100.00)
+        (rect 0.00 400.00 200.00 100.00)
+        (rect 0.00 300.00 200.00 100.00)
         (rect 0.00 200.00 200.00 100.00)
         (rect 0.00 100.00 200.00 100.00)
       )
@@ -123,6 +126,9 @@ CASE 4, scrolling y to 170 new layers will be squashed, so things repaint:
       (contentsOpaque 1)
       (drawsContent 1)
       (repaint rects
+        (rect 0.00 600.00 200.00 100.00)
+        (rect 0.00 500.00 200.00 100.00)
+        (rect 0.00 400.00 200.00 100.00)
         (rect 0.00 300.00 200.00 100.00)
         (rect 0.00 200.00 200.00 100.00)
       )