Introduce RenderNodeWithChildMixin

sky/tests/raw/render_box.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 '../resources/third_party/unittest/unittest.dart';
 import '../resources/unit.dart';
 import 'dart:sky' as sky;
 import 'package:sky/framework/layout2.dart';
 
 class RenderSizedBox extends RenderBox {
@@ skipping 14 matching lines @@
     height = constraints.constrainHeight(desiredHeight);
     layoutDone();
   }
 }
 
 void main() {
   initUnit();
 
   test("should size to render view", () {
     RenderSizedBox root = new RenderSizedBox();
-    RenderView renderView = new RenderView(root: root);
+    RenderView renderView = new RenderView(child: root);
     renderView.layout(newWidth: sky.view.width, newHeight: sky.view.height);
     expect(root.width, equals(sky.view.width));
     expect(root.height, equals(sky.view.height));
   });
 }