Replace setBoxDecoration() with a decoration property.

sky/examples/raw/simple_render_tree.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:sky';
 import 'package:sky/framework/app.dart';
 import 'package:sky/framework/layout2.dart';
 
 class RenderSolidColor extends RenderDecoratedBox {
   final double desiredHeight;
@@ skipping 12 matching lines @@
   }
 
   void layout(BoxConstraints constraints, { RenderNode relayoutSubtreeRoot }) {
     width = constraints.constrainWidth(desiredWidth);
     height = constraints.constrainHeight(desiredHeight);
     layoutDone();
   }
 
   void handlePointer(PointerEvent event) {
     if (event.type == 'pointerdown')
-      setBoxDecoration(new BoxDecoration(backgroundColor: 0xFFFF0000));
+      decoration = new BoxDecoration(backgroundColor: 0xFFFF0000);
     else if (event.type == 'pointerup')
-      setBoxDecoration(new BoxDecoration(backgroundColor: backgroundColor));
+      decoration = new BoxDecoration(backgroundColor: backgroundColor);
   }
 }
 
 AppView app;
 
 void main() {
   var root = new RenderFlex(
       direction: FlexDirection.Vertical,
       decoration: new BoxDecoration(backgroundColor: 0xFF000000));
 
@@ skipping 26 matching lines @@
   // Purple and blue cells
   addFlexChild(row, 0x77FF00FF, flex: 1);
   addFlexChild(row, 0xFF0000FF, flex: 2);
 
   root.add(row);
   row.parentData.flex = 3;
 
   app = new AppView(root);
 
 }