Disable solid background color optimization for composited layers.

LayoutTests/compositing/overflow/clip-descendents-expected.txt

Index: LayoutTests/compositing/overflow/clip-descendents-expected.txt
diff --git a/LayoutTests/compositing/overflow/clip-descendents-expected.txt b/LayoutTests/compositing/overflow/clip-descendents-expected.txt
index 129b81d319c79b910c1eabe5c16dc2d6b5d7dbf4..916365a6245438b24b73c6d744c7784ab0e833ea 100644
--- a/LayoutTests/compositing/overflow/clip-descendents-expected.txt
+++ b/LayoutTests/compositing/overflow/clip-descendents-expected.txt
@@ -13,6 +13,8 @@
               (position 2.00 12.00)
               (bounds 100.00 150.00)
               (contentsOpaque 1)
+              (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])
             )
           )
@@ -25,6 +27,8 @@
               (position 2.00 12.00)
               (bounds 100.00 150.00)
               (contentsOpaque 1)
+              (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])
             )
           )
@@ -40,6 +44,8 @@
                   (position 2.00 12.00)
                   (bounds 100.00 150.00)
                   (contentsOpaque 1)
+                  (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])
                 )
               )
@@ -57,6 +63,8 @@
                   (position 2.00 12.00)
                   (bounds 100.00 150.00)
                   (contentsOpaque 1)
+                  (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])
                 )
               )