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

samples/third_party/todomvc/web/elements/td_item.dart

+library todomvc.web.elements.td_item;
+
+import 'dart:html';
+import 'package:polymer/polymer.dart';
+import 'td_model.dart';
+
+@CustomTag('td-item')
+class TodoItem extends LIElement with Polymer, Observable {
+  @observable bool editing = false;
+  @observable Todo item;
+
+  factory TodoItem() => new Element.tag('li', 'td-item');
+  TodoItem.created() : super.created() { polymerCreated(); }
+
+  editAction() {
+    editing = true;
+    // schedule focus for the end of microtask, when the input will be visible
+    async((_) => $['edit'].focus());
+  }
+
+  commitAction() {
+    if (editing) {
+      editing = false;
+      item.title = item.title.trim();
+      if (item.title == '') {
+        destroyAction();
+      }
+      fire('td-item-changed');
+    }
+  }
+
+  cancelAction() {
+    editing = false;
+  }
+
+  itemChangeAction() {
+    // TODO(jmesserly): asyncFire is needed because "click" fires before
+    // "item.checked" is updated on Firefox. Need to check Polymer.js.
+    asyncFire('td-item-changed');
+  }
+
+  destroyAction() {
+    fire('td-destroy-item', detail: item);
+  }
+}