Make Icon work using space-aged base-url technology.

sky/sdk/lib/framework/components2/icon.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 '../fn2.dart';
 import '../rendering/box.dart';
 
 // TODO(eseidel): This should use package:.
 const String kAssetBase = '/packages/sky/assets/material-design-icons';
 
 class Icon extends Component {
-  double size;
+  int size;
   String type;
 
   Icon({
     String key,
     this.size,
     this.type: ''
   }) : super(key: key);
 
   UINode build() {
     String category = '';
     String subtype = '';
     List<String> parts = type.split('/');
     if (parts.length == 2) {
       category = parts[0];
       subtype = parts[1];
     }
     return new Image(
-      size: new sky.Size(size, size),
+      size: new sky.Size(size.toDouble(), size.toDouble()),
       src: '${kAssetBase}/${category}/2x_web/ic_${subtype}_${size}dp.png'
     );
   }
 }