Add a shadow to the FloatingActionButton.

sky/sdk/lib/framework/components2/floating_action_button.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 '../fn2.dart';
 import '../rendering/box.dart';
+import '../painting/shadows.dart';
 import '../theme2/colors.dart';
 import 'dart:sky' as sky;
 import 'ink_well.dart';
 import 'material.dart';
 
 const double _kSize = 56.0;
 
 class FloatingActionButton extends Component {
   UINode content;
   int level;
 
   FloatingActionButton({ Object key, this.content, this.level: 0 })
       : super(key: key);
 
   UINode build() {
     List<UINode> children = [];
 
     if (content != null)
       children.add(content);
 
     return new Material(
       content: new CustomPaint(
         callback: (sky.Canvas canvas) {
           const double radius = _kSize / 2.0;
-          canvas.drawCircle(radius, radius, radius, new sky.Paint()..color = Red[500]);
+          sky.Paint paint = new sky.Paint()..color = Red[500];
+          var builder = new ShadowDrawLooperBuilder()
+            ..addShadow(const sky.Size(0.0, 5.0),
+                        const sky.Color(0x77000000),
+                        5.0);
+          paint.setDrawLooper(builder.build());
+          canvas.drawCircle(radius, radius, radius, paint);
         },
         child: new Container(
           width: _kSize,
           height: _kSize,
           child: new InkWell(children: children))),
       level: level);
   }
 }