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

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

+library todomvc.web.elements.td_todos;
+
+import 'dart:html';
+import 'package:polymer/polymer.dart';
+import 'td_input.dart';
+import 'td_model.dart';
+
+@CustomTag('td-todos')
+class TodoList extends PolymerElement {
+  @published String modelId;
+  @published String route;
+
+  @observable TodoModel model;
+  @observable String activeRoute;
+
+  factory TodoList() => new Element.tag('td-todos');
+  TodoList.created() : super.created();
+
+  TodoInput get _newTodo => $['new-todo'];
+
+  void modelIdChanged() {
+    model = document.querySelector('#$modelId');
+  }
+
+  void routeChanged() {
+    if (model != null) model.filter = route;
+
+    // TODO(jmesserly): polymer_expressions lacks boolean conversions.
+    activeRoute = (route != null && route != '') ? route : 'all';
+  }
+
+  void addTodoAction() {
+    model.newItem(_newTodo.value);
+    // when polyfilling Object.observe, make sure we update immediately
+    Observable.dirtyCheck();
+    _newTodo.value = '';
+  }
+
+  void cancelAddTodoAction() {
+    _newTodo.value = '';
+  }
+
+  void itemChangedAction() {
+    if (model != null) model.itemsChanged();
+  }
+
+  void destroyItemAction(e, detail) {
+    model.destroyItem(detail);
+  }
+
+  void toggleAllCompletedAction(e, detail, sender) {
+    model.setItemsCompleted(sender.checked);
+  }
+
+  void clearCompletedAction() {
+    model.clearItems();
+  }
+
+  // TODO(jmesserly): workaround for HTML Imports not setting correct baseURI
+  String get baseUri =>  declaration.ownerDocument == document ? '../' : '';
+}