Implement Container in fn2

sky/examples/fn2/container.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' as sky;
 import 'package:sky/framework/fn2.dart';
+import 'package:sky/framework/rendering/box.dart';
 
 class ContainerApp extends App {
   UINode build() {
     return new EventListenerNode(
       new BlockContainer(children: [
         new Rectangle(0xFF00FFFF, key: 1),
-        new Rectangle(0xFF00FF00, key: 2),
+        new Container(
+          padding: new EdgeDims.all(10.0),
+          margin: new EdgeDims.all(10.0),
+          desiredSize: new sky.Size(double.INFINITY, 100.0),

[Hixie, 2015/06/02 21:52:21]

why not desiredWidth and desiredHeight separately? I expect we'll almost always
be only giving one, and it gets buried in all the "new
Sky.Size(double.INFINITY...) boilerplate here.

+          decoration: new BoxDecoration(backgroundColor: 0xFF00FF00),
+          child: new BlockContainer(

[Hixie, 2015/06/02 21:52:21]

Why the BlockContainer, since it only has one child?

+              children: [
+                  new Container(
+                      decoration: new BoxDecoration(backgroundColor: 0xFFFFFF00),
+                      desiredSize: new sky.Size(double.INFINITY, 20.0)
+                  )
+              ])),
         new Rectangle(0xFF0000FF, key: 3)
       ]),
       onPointerDown: _handlePointerDown);
   }
 
   void _handlePointerDown(sky.PointerEvent event) {
     print("_handlePointerDown");
   }
 }
 
 void main() {
   new ContainerApp();
 }