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

samples/third_party/todomvc/web/model.dart

-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
-// for details. 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.model;
-
-import 'package:polymer/polymer.dart';
-
-final appModel = new AppModel._();
-
-@reflectable
-class AppModel extends Observable {
-  final ObservableList<Todo> todos = new ObservableList<Todo>();
-  @observable int doneCount;
-  @observable int remaining;
-  @observable List<Todo> visibleTodos;
-  @observable bool hasCompleteTodos;
-
-  bool _allChecked;
-
-  AppModel._() {
-    new ListPathObserver(todos, 'done').changes.listen(_updateTodoDone);
-    windowLocation.changes.listen(_updateVisibleTodos);
-    _updateTodoDone(null);
-  }
-
-  _updateTodoDone(_) {
-    // TODO(jmesserly): we should try using Polymer Expressions and filters
-    // instead of computing so many things.
-    doneCount = todos.fold(0, (count, t) => count + (t.done ? 1 : 0));
-    hasCompleteTodos = doneCount > 0;
-    remaining = todos.length - doneCount;
-
-    _allChecked = notifyPropertyChange(const Symbol('allChecked'),
-        _allChecked, todos.length > 0 && remaining == 0);
-
-    _updateVisibleTodos(_);
-  }
-
-  _updateVisibleTodos(_) {
-    bool filterDone = null;
-    if (windowLocation.hash == '#/completed') {
-      filterDone = true;
-    } else if (windowLocation.hash == '#/active') {
-      filterDone = false;
-    }
-
-    visibleTodos = todos.where(
-        (t) => filterDone == null || t.done == filterDone)
-        .toList(growable: false);
-  }
-
-  // TODO(jmesserly): the @observable here is temporary.
-  bool get allChecked => _allChecked;
-  set allChecked(bool value) {
-    todos.forEach((t) { t.done = value; });
-  }
-
-  void clearDone() => todos.removeWhere((t) => t.done);
-}
-
-class Todo extends Observable {
-  @observable String task;
-  @observable bool done = false;
-
-  Todo(this.task);
-
-  String toString() => "$task ${done ? '(done)' : '(not done)'}";
-}