Introduce RenderNodeWithChildMixin

sky/tests/raw/render_box.dart

Index: sky/tests/raw/render_box.dart
diff --git a/sky/tests/raw/render_box.dart b/sky/tests/raw/render_box.dart
index 76ac54c3b5838eefef01d6939066c3865919ecc9..c3d3412767ce15a14f62a4fad95ed38b3685caae 100644
--- a/sky/tests/raw/render_box.dart
+++ b/sky/tests/raw/render_box.dart
@@ -32,7 +32,7 @@ void main() {
 
   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));