Implement will-change-based creation of layers, stacking contexts, and containing blocks

LayoutTests/compositing/will-change/composited-layers-expected.txt

Index: LayoutTests/compositing/will-change/composited-layers-expected.txt
diff --git a/LayoutTests/compositing/will-change/composited-layers-expected.txt b/LayoutTests/compositing/will-change/composited-layers-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..4caf3b3804d495644799919d895a49494cfb70b7
--- /dev/null
+++ b/LayoutTests/compositing/will-change/composited-layers-expected.txt
@@ -0,0 +1,53 @@
+(GraphicsLayer
+  (bounds 800.00 600.00)
+  (children 1
+    (GraphicsLayer
+      (bounds 800.00 600.00)
+      (contentsOpaque 1)
+      (drawsContent 1)
+      (children 8
+        (GraphicsLayer
+          (position 60.00 0.00)
+          (bounds 50.00 50.00)
+          (contentsOpaque 1)
+        )
+        (GraphicsLayer
+          (position 120.00 0.00)
+          (bounds 50.00 50.00)
+          (contentsOpaque 1)
+        )
+        (GraphicsLayer
+          (position 180.00 0.00)
+          (bounds 50.00 50.00)
+          (contentsOpaque 1)
+        )
+        (GraphicsLayer
+          (position 240.00 0.00)
+          (bounds 50.00 50.00)
+          (contentsOpaque 1)
+        )
+        (GraphicsLayer
+          (position 0.00 60.00)
+          (bounds 50.00 50.00)
+          (contentsOpaque 1)
+        )
+        (GraphicsLayer
+          (position 60.00 60.00)
+          (bounds 50.00 50.00)
+          (contentsOpaque 1)
+        )
+        (GraphicsLayer
+          (position 120.00 60.00)
+          (bounds 50.00 50.00)
+          (contentsOpaque 1)
+        )
+        (GraphicsLayer
+          (position 180.00 60.00)
+          (bounds 50.00 50.00)
+          (contentsOpaque 1)
+        )
+      )
+    )
+  )
+)
+