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/slide_puzzle/lib/src/theme_simple.dart

@@ -1,9 +1,6 @@
-// Copyright 2019 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 'package:flutter/material.dart';
 
-import 'core/puzzle_proxy.dart';
-import 'flutter.dart';
+import 'app_state.dart';
 import 'shared_theme.dart';
 
 const _accentBlue = Color(0xff000579e);
@@ -12,7 +9,7 @@ class ThemeSimple extends SharedTheme {
   @override
   String get name => 'Simple';
 
-  const ThemeSimple();
+  ThemeSimple(AppState proxy) : super(proxy);
 
   @override
   Color get puzzleThemeBackground => Colors.white;
@@ -24,8 +21,7 @@ class ThemeSimple extends SharedTheme {
   Color get puzzleAccentColor => _accentBlue;
 
   @override
-  RoundedRectangleBorder puzzleBorder(bool small) =>
-      const RoundedRectangleBorder(
+  RoundedRectangleBorder get puzzleBorder => const RoundedRectangleBorder(
         side: BorderSide(color: Colors.black26, width: 1),
         borderRadius: BorderRadius.all(
           Radius.circular(4),
@@ -33,7 +29,7 @@ class ThemeSimple extends SharedTheme {
       );
 
   @override
-  Widget tileButton(int i, PuzzleProxy puzzle, bool small) {
+  Widget tileButton(int i) {
     if (i == puzzle.tileCount) {
       assert(puzzle.solved);
       return const Center(
@@ -54,15 +50,13 @@ class ThemeSimple extends SharedTheme {
           style: TextStyle(
             color: Colors.white,
             fontWeight: correctPosition ? FontWeight.bold : FontWeight.normal,
-            fontSize: small ? 30 : 49,
+            fontSize: 49,
           ),
         ),
       ),
     );
 
     return createButton(
-      puzzle,
-      small,
       i,
       content,
       color: const Color.fromARGB(255, 13, 87, 155),