Drop background color optimization for composited layers

LayoutTests/compositing/squashing/squash-above-fixed-2-expected.txt

Index: LayoutTests/compositing/squashing/squash-above-fixed-2-expected.txt
diff --git a/LayoutTests/compositing/squashing/squash-above-fixed-2-expected.txt b/LayoutTests/compositing/squashing/squash-above-fixed-2-expected.txt
index 68d98107099b22cbebaa3d1b5e5bce9cebce357e..6651a7be9855263bb74021524d4bc0a257e0d84c 100644
--- a/LayoutTests/compositing/squashing/squash-above-fixed-2-expected.txt
+++ b/LayoutTests/compositing/squashing/squash-above-fixed-2-expected.txt
@@ -12,10 +12,14 @@ CASE 1, original layer tree:
         (GraphicsLayer
           (bounds 400.00 200.00)
           (contentsOpaque 1)
+          (drawsContent 1)
+          (backgroundColor #0000FF)
           (children 1
             (GraphicsLayer
               (bounds 50.00 50.00)
               (contentsOpaque 1)
+              (drawsContent 1)
+              (backgroundColor #FF0000)
             )
           )
         )
@@ -23,6 +27,8 @@ CASE 1, original layer tree:
           (position 100.00 50.00)
           (bounds 200.00 4000.00)
           (contentsOpaque 1)
+          (drawsContent 1)
+          (backgroundColor #00FFFF)
         )
       )
     )
@@ -41,10 +47,14 @@ CASE 2, scrolling y to 80, the "container" element should remain positioned with
           (position 0.00 80.00)
           (bounds 400.00 200.00)
           (contentsOpaque 1)
+          (drawsContent 1)
+          (backgroundColor #0000FF)
           (children 1
             (GraphicsLayer
               (bounds 50.00 50.00)
               (contentsOpaque 1)
+              (drawsContent 1)
+              (backgroundColor #FF0000)
             )
           )
         )
@@ -52,6 +62,8 @@ CASE 2, scrolling y to 80, the "container" element should remain positioned with
           (position 100.00 50.00)
           (bounds 200.00 4000.00)
           (contentsOpaque 1)
+          (drawsContent 1)
+          (backgroundColor #00FFFF)
         )
       )
     )