Update web/ samples to work with Flutter SDK (#134)

* add package:http dependency in dad_jokes

* add package:http dependency in filipino_cuisine

* don't build package:http demos until flutter/flutter#34858 is resolved

* update gallery

* update github_dataviz

* update particle_background

* don't build github_dataviz (uses package:http)

* update slide_puzzle

* update spinning_square

* update timeflow

* update vision_challenge

* update charts

* update dad_jokes

* update filipino cuisine

* ignore build output

* update timeflow and vision_challenge

* update slide_puzzle

* don't commit build/ directory

* move preview.png images to assets

* fix path url join

* update readme

* update web/readme.md

web/gallery/lib/demo/material/overscroll_demo.dart

@@ -1,17 +1,17 @@
-// Copyright 2018 The Chromium Authors. All rights reserved.
+// Copyright 2016 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 'package:flutter_web/material.dart';
+import 'package:flutter/material.dart';
 
 import '../../gallery/demo.dart';
 
 enum IndicatorType { overscroll, refresh }
 
 class OverscrollDemo extends StatefulWidget {
-  const OverscrollDemo({Key key}) : super(key: key);
+  const OverscrollDemo({ Key key }) : super(key: key);
 
   static const String routeName = '/material/overscroll';
 
@@ -21,38 +21,24 @@ class OverscrollDemo extends StatefulWidget {
 
 class OverscrollDemoState extends State<OverscrollDemo> {
   final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
-  final GlobalKey<RefreshIndicatorState> _refreshIndicatorKey =
-      GlobalKey<RefreshIndicatorState>();
+  final GlobalKey<RefreshIndicatorState> _refreshIndicatorKey = GlobalKey<RefreshIndicatorState>();
   static final List<String> _items = <String>[
-    'A',
-    'B',
-    'C',
-    'D',
-    'E',
-    'F',
-    'G',
-    'H',
-    'I',
-    'J',
-    'K',
-    'L',
-    'M',
-    'N'
+    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
   ];
 
   Future<void> _handleRefresh() {
     final Completer<void> completer = Completer<void>();
-    Timer(const Duration(seconds: 3), () {
-      completer.complete();
-    });
+    Timer(const Duration(seconds: 3), () { completer.complete(); });
     return completer.future.then<void>((_) {
       _scaffoldKey.currentState?.showSnackBar(SnackBar(
-          content: const Text('Refresh complete'),
-          action: SnackBarAction(
-              label: 'RETRY',
-              onPressed: () {
-                _refreshIndicatorKey.currentState.show();
-              })));
+        content: const Text('Refresh complete'),
+        action: SnackBarAction(
+          label: 'RETRY',
+          onPressed: () {
+            _refreshIndicatorKey.currentState.show();
+          },
+        ),
+      ));
     });
   }
 
@@ -60,31 +46,36 @@ class OverscrollDemoState extends State<OverscrollDemo> {
   Widget build(BuildContext context) {
     return Scaffold(
       key: _scaffoldKey,
-      appBar: AppBar(title: const Text('Pull to refresh'), actions: <Widget>[
-        MaterialDemoDocumentationButton(OverscrollDemo.routeName),
-        IconButton(
+      appBar: AppBar(
+        title: const Text('Pull to refresh'),
+        actions: <Widget>[
+          MaterialDemoDocumentationButton(OverscrollDemo.routeName),
+          IconButton(
             icon: const Icon(Icons.refresh),
             tooltip: 'Refresh',
             onPressed: () {
               _refreshIndicatorKey.currentState.show();
-            }),
-      ]),
+            },
+          ),
+        ],
+      ),
       body: RefreshIndicator(
         key: _refreshIndicatorKey,
         onRefresh: _handleRefresh,
-        child: ListView.builder(
-          padding: kMaterialListPadding,
-          itemCount: _items.length,
-          itemBuilder: (BuildContext context, int index) {
-            final String item = _items[index];
-            return ListTile(
-              isThreeLine: true,
-              leading: CircleAvatar(child: Text(item)),
-              title: Text('This item represents $item.'),
-              subtitle: const Text(
-                  'Even more additional list item information appears on line three.'),
-            );
-          },
+        child: Scrollbar(
+          child: ListView.builder(
+            padding: kMaterialListPadding,
+            itemCount: _items.length,
+            itemBuilder: (BuildContext context, int index) {
+              final String item = _items[index];
+              return ListTile(
+                isThreeLine: true,
+                leading: CircleAvatar(child: Text(item)),
+                title: Text('This item represents $item.'),
+                subtitle: const Text('Even more additional list item information appears on line three.'),
+              );
+            },
+          ),
         ),
       ),
     );