Update TodoMVC based on https://github.com/polymer/todomvc

samples/third_party/todomvc/web/lib-elements/polymer_localstorage.dart

+// Copyright 2013 The Polymer Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+library todomvc.web.lib_elements.polymer_localstorage;
+
+import 'dart:convert' show JSON;
+import 'dart:html';
+import 'package:polymer/polymer.dart';
+
+@CustomTag('polymer-localstorage')
+class PolymerLocalStorage extends PolymerElement {
+  @observable bool useRaw = false;
+  @observable String name;
+  @observable var value;
+
+  factory PolymerLocalStorage() => new Element.tag('polymer-localstorage');
+  PolymerLocalStorage.created() : super.created();
+
+  void ready() {
+    load();
+  }
+
+  void valueChanged() {
+    save();
+  }
+
+  void load() {
+    var s = window.localStorage[name];
+    if (s != null && !useRaw) {
+      value = JSON.decode(s);
+    } else {
+      value = s;
+    }
+  }
+
+  void save() {
+    window.localStorage[name] = useRaw ? value : JSON.encode(value);
+  }
+}