Add a manual test app for animated icons (#14272)

dev/manual_tests/lib/animated_icons.dart

+// Copyright 2018 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';
+
+class AnimatedIconsTestApp extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return new MaterialApp(
+      title: 'Animated Icons Test',
+      home: const Scaffold(
+        body: const IconsList(),
+      ),
+    );
+  }
+}
+
+class IconsList extends StatelessWidget {
+  const IconsList();
+
+  @override
+  Widget build(BuildContext context) {
+    return new ListView(
+      children: samples.map((IconSample s) => new IconSampleRow(s)).toList(),
+    );
+  }
+}
+
+class IconSampleRow extends StatefulWidget {
+  const IconSampleRow(this.sample);
+
+  final IconSample sample;
+
+  @override
+  State createState() => new IconSampleRowState();
+}
+
+class IconSampleRowState extends State<IconSampleRow> with SingleTickerProviderStateMixin {
+  AnimationController progress;
+
+  @override
+  Widget build(BuildContext context) {
+    return new ListTile(
+      leading: new InkWell(
+        onTap: () { progress.forward(from: 0.0); },
+        child: new AnimatedIcon(
+          icon: widget.sample.icon,
+          progress: progress,
+          color: Colors.lightBlue,
+        ),
+      ),
+      title: new Text(widget.sample.description),
+      subtitle: new Slider(
+        value: progress.value,
+        onChanged: (double v) { progress.animateTo(v, duration: Duration.ZERO); },
+      ),
+    );
+  }
+
+  @override
+  void initState() {
+    super.initState();
+    progress = new AnimationController(vsync: this, duration: const Duration(milliseconds: 300));
+    progress.addListener(_handleChange);
+  }
+
+  @override
+  void dispose() {
+    progress.removeListener(_handleChange);
+    super.dispose();
+  }
+
+  void _handleChange() {
+    setState(() {});
+  }
+}
+
+const List<IconSample> samples = const <IconSample> [
+  const IconSample(AnimatedIcons.arrow_menu, 'arrow_menu'),
+  const IconSample(AnimatedIcons.menu_arrow, 'menu_arrow'),
+];
+
+class IconSample {
+  const IconSample(this.icon, this.description);
+  final AnimatedIconData icon;
+  final String description;
+}
+
+void main() => runApp(new AnimatedIconsTestApp());