Refactor stateful parts of Component into StatefulComponent

sky/sdk/lib/widgets/basic.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:async';
 import 'dart:sky' as sky;
 
 import 'package:vector_math/vector_math.dart';
 
 import '../mojo/asset_bundle.dart';
 import '../mojo/net/image_cache.dart' as image_cache;
 import '../painting/text_style.dart';
 import '../rendering/block.dart';
 import '../rendering/box.dart';
 import '../rendering/flex.dart';
 import '../rendering/object.dart';
 import '../rendering/paragraph.dart';
 import '../rendering/stack.dart';
 import 'default_text_style.dart';
 import 'widget.dart';
 
 export '../rendering/box.dart' show BackgroundImage, BoxConstraints, BoxDecoration, Border, BorderSide, EdgeDims;
 export '../rendering/flex.dart' show FlexDirection, FlexJustifyContent, FlexAlignItems;
 export '../rendering/object.dart' show Point, Offset, Size, Rect, Color, Paint, Path;
-export 'widget.dart' show Widget, Component, App, runApp, Listener, ParentDataNode;
+export 'widget.dart' show Widget, Component, StatefulComponent, App, runApp, Listener, ParentDataNode;
 
 
 // PAINTING NODES
 
 class Opacity extends OneChildRenderObjectWrapper {
   Opacity({ String key, this.opacity, Widget child })
     : super(key: key, child: child);
 
   RenderOpacity get root => super.root;
   final double opacity;
@@ skipping 462 matching lines @@
   final sky.Image image;
   final Size size;
 
   void syncRenderObject(Widget old) {
     super.syncRenderObject(old);
     root.image = image;
     root.requestedSize = size;
   }
 }
 
-class FutureImage extends Component {
-  FutureImage({ this.image, this.size }) : super(stateful: true);
+class FutureImage extends StatefulComponent {
+  FutureImage({ this.image, this.size });
 
   Future<sky.Image> image;
   Size size;
   sky.Image _resolvedImage;
 
   void didMount() {
     super.didMount();
     _resolveImage();
   }
 
@@ skipping 64 matching lines @@
   }
 
   void remove() {
     RenderObjectWrapper ancestor = findAncestor(RenderObjectWrapper);
     assert(ancestor is RenderObjectWrapper);
     ancestor.detachChildRoot(this);
     super.remove();
   }
 
 }