Use AnimatedContainer for card_collection.dart.

sky/sdk/lib/widgets/material.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 '../animation/animation_performance.dart';
 import '../painting/box_painter.dart';
 import 'animated_component.dart';
 import 'animated_container.dart';
 import 'basic.dart';
 import 'default_text_style.dart';
@@ skipping 20 matching lines @@
     int level: 0,
     Color color: null
   }) : super(key: key) {
     if (level == null) level = 0;
     _container = new AnimatedContainer()
       ..shadow = new AnimatedType<double>(level.toDouble())
       ..backgroundColor = new AnimatedColor(_getBackgroundColor(type, color))
       ..borderRadius = edges[type]
       ..shape = type == MaterialType.circle ? Shape.circle : Shape.rectangle;
     watchPerformance(_container.createPerformance(
-        _container.shadow, duration: _kAnimateShadowDuration));
+        [_container.shadow], duration: _kAnimateShadowDuration));
     watchPerformance(_container.createPerformance(
-        _container.backgroundColor, duration: _kAnimateColorDuration));
+        [_container.backgroundColor], duration: _kAnimateColorDuration));
   }
 
   Widget child;
 
   AnimatedContainer _container;
 
   void syncFields(Material source) {
     child = source.child;
     _container.syncFields(source._container);
     super.syncFields(source);
@@ skipping 12 matching lines @@
     }
   }
 
   Widget build() {
     return _container.build(
         new DefaultTextStyle(style: Theme.of(this).text.body1, child: child)
     );
   }
 
 }