fixes for latest SDK

example/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 model;
 
 import 'dart:html' show CompoundBinding;
 import 'package:polymer/polymer.dart';
 
 final appModel = new AppModel._();
 
 class AppModel extends ObservableBase {
   final ObservableList<Todo> todos = new ObservableList<Todo>();
   @observable int doneCount;
   @observable int remaining;
   @observable List<Todo> visibleTodos;
-  @observable bool hasTodos;
   @observable bool hasCompleteTodos;
 
   bool _allChecked;
 
   AppModel._() {
-    // TODO(jmesserly): need to make this easier.
     new ListPathObserver(todos, 'done').changes.listen(_updateTodoDone);
     windowLocation.changes.listen(_updateVisibleTodos);
     _updateTodoDone(null);
   }
 
   _updateTodoDone(_) {
+    // TODO(jmesserly): we should try using fancy-syntax 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;
-    hasTodos = todos.length > 0;
 
     _allChecked = notifyPropertyChange(const Symbol('allChecked'),
-        _allChecked, hasTodos && remaining == 0);
+        _allChecked, todos.length > 0 && remaining == 0);
 
     _updateVisibleTodos(_);
   }
 
   _updateVisibleTodos(_) {
     bool filterDone = null;
     if (windowLocation.hash == '#/completed') {
       filterDone = true;
     } else if (windowLocation.hash == '#/active') {
       filterDone = false;
@@ skipping 14 matching lines @@
 }
 
 class Todo extends ObservableBase {
   @observable String task;
   @observable bool done = false;
 
   Todo(this.task);
 
   String toString() => "$task ${done ? '(done)' : '(not done)'}";
 }