Add flutter_web samples (#75)

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

@@ -0,0 +1,92 @@
+// 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_web/material.dart';
+
+class EditableTextDemo extends StatefulWidget {
+  static String routeName = '/material/editable_text';
+
+  @override
+  State<StatefulWidget> createState() => EditableTextDemoState();
+}
+
+class EditableTextDemoState extends State<EditableTextDemo> {
+  final cyanController = TextEditingController(text: 'Cyan');
+  final orangeController = TextEditingController(text: 'Orange');
+  final thickController = TextEditingController(text: 'Thick Rounded Cursor');
+  final multiController =
+      TextEditingController(text: 'First line\nSecond line');
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text('Text Editing'),
+        centerTitle: true,
+      ),
+      body: ListView(
+        children: [
+          field(
+            cyanController,
+            color: Colors.cyan.shade50,
+            selection: Colors.cyan.shade200,
+            cursor: Colors.cyan.shade900,
+          ),
+          field(
+            orangeController,
+            color: Colors.orange.shade50,
+            selection: Colors.orange.shade200,
+            cursor: Colors.orange.shade900,
+            center: true,
+          ),
+          field(
+            thickController,
+            color: Colors.white,
+            selection: Colors.grey.shade200,
+            cursor: Colors.red.shade900,
+            radius: const Radius.circular(2),
+            cursorWidth: 8,
+          ),
+          Banner(
+            child: TextField(
+              style: TextStyle(fontWeight: FontWeight.bold, fontSize: 20),
+              controller: multiController,
+              maxLines: 3,
+            ),
+            message: 'W.I.P',
+            textDirection: TextDirection.ltr,
+            location: BannerLocation.bottomEnd,
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+Widget field(
+  TextEditingController controller, {
+  Color color,
+  Color selection,
+  Color cursor,
+  Radius radius = null,
+  double cursorWidth = 2,
+  bool center = false,
+}) {
+  return Theme(
+    data: ThemeData(textSelectionColor: selection),
+    child: Container(
+      color: color,
+      child: TextField(
+        textAlign: center ? TextAlign.center : TextAlign.start,
+        decoration: InputDecoration(
+          contentPadding: EdgeInsets.fromLTRB(8, 16, 8, 16),
+        ),
+        controller: controller,
+        cursorColor: cursor,
+        cursorRadius: radius,
+        cursorWidth: cursorWidth,
+      ),
+    ),
+  );
+}