Address Ian's comments on layout2.dart

sky/examples/raw/simple_render_tree.dart

Index: sky/examples/raw/simple_render_tree.dart
diff --git a/sky/examples/raw/simple_render_tree.dart b/sky/examples/raw/simple_render_tree.dart
index 205043523b38ea524a254e9e60ed5f65700c7305..555c8757ef30bb8690999ca7280a066a216f900b 100644
--- a/sky/examples/raw/simple_render_tree.dart
+++ b/sky/examples/raw/simple_render_tree.dart
@@ -18,8 +18,8 @@ class RenderSolidColor extends RenderDecoratedBox {
   }
 
   void layout(BoxConstraints constraints, { RenderNode relayoutSubtreeRoot }) {
-    setWidth(constraints, constraints.maxWidth);
-    setHeight(constraints, 200.0);
+    width = constraints.constrainWidth(constraints.maxWidth);
+    height = constraints.constrainHeight(200.0);
     layoutDone();
   }