Make RenderBlock painting match its hittesting

sky/sdk/example/demo_launcher/lib/main.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';
 
 import 'package:sky/mojo/activity.dart' as activity;
 import 'package:sky/mojo/asset_bundle.dart';
 import 'package:sky/mojo/shell.dart' as shell;
 import 'package:sky/painting/box_painter.dart';
 import 'package:sky/theme/colors.dart' as colors;
 import 'package:sky/theme/typography.dart' as typography;
 import 'package:sky/widgets/basic.dart';
 import 'package:sky/widgets/card.dart';
 import 'package:sky/widgets/fixed_height_scrollable.dart';
 import 'package:sky/widgets/flat_button.dart';
 import 'package:sky/widgets/material.dart';
 import 'package:sky/widgets/scaffold.dart';
 import 'package:sky/widgets/task_description.dart';
 import 'package:sky/widgets/theme.dart';
 import 'package:sky/widgets/tool_bar.dart';
+import 'package:sky/widgets/scrollable_list.dart';
 
 AssetBundle _initBundle() {
   if (rootBundle != null)
     return rootBundle;
   const String _kAssetBase = '..';
   return new NetworkAssetBundle(Uri.base.resolve(_kAssetBase));
 }
 
 final AssetBundle _bundle = _initBundle();
 
@@ skipping 93 matching lines @@
     textTheme: typography.white
   ),
 
   // TODO(jackson): This doesn't seem to be working
   // new SkyDemo('Licenses', 'LICENSES.sky'),
 ];
 
 const double kCardHeight = 120.0;
 const EdgeDims kListPadding = const EdgeDims.all(4.0);
 
-class DemoList extends FixedHeightScrollable {
-  DemoList({ String key }) : super(key: key, itemHeight: kCardHeight, padding: kListPadding);
-
-  int get itemCount => demos.length;
-
+class DemoList extends Component {
   Widget buildDemo(SkyDemo demo) {
     return new Listener(
       key: demo.name,
       onGestureTap: (_) => launch(demo.href, demo.bundle),
       child: new Container(
         height: kCardHeight,
         child: new Card(
           child: new Flex([
             new Flexible(
               child: new Stack([
                 new Container(
                   decoration: demo.decoration,
                   child: new Container()
                 ),
                 new Container(
                   margin: const EdgeDims.all(24.0),
                   child: new Block([
                     new Text(demo.name, style: demo.textTheme.title),
                     new Text(demo.description, style: demo.textTheme.subhead)
                   ])
                 )
               ])
             ),
           ], direction: FlexDirection.vertical)
         )
       )
     );
   }
 
-  List<Widget> buildItems(int start, int count) {
-    return demos
-      .skip(start)
-      .take(count)
-      .map(buildDemo)
-      .toList(growable: false);
+  Widget build() {
+    return new ScrollableList<SkyDemo>(
+      items: demos,
+      itemHeight: kCardHeight,
+      itemBuilder: buildDemo,
+      padding: kListPadding
+    );
   }
 }
 
 class SkyHome extends App {
   Widget build() {
     return new Theme(
       data: new ThemeData(
         brightness: ThemeBrightness.dark,
         primarySwatch: colors.Teal
       ),
       child: new TaskDescription(
         label: 'Sky Demos',
         child: new Scaffold(
           toolbar: new ToolBar(center: new Text('Sky Demos')),
           body: new Material(
             type: MaterialType.canvas,
             child: new DemoList()
           )
         )
       )
     );
   }
 }
 
 void main() {
   runApp(new SkyHome());
 }