update elements and fix some bugs

test/iron_collapse_test.dart

 // Copyright (c) 2015, 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.
 @TestOn('browser')
 library polymer_elements.test.iron_collapse_test;
 
 import 'dart:async';
 import 'package:polymer_elements/iron_collapse.dart';
 import 'package:test/test.dart';
 import 'package:web_components/web_components.dart';
@@ skipping 42 matching lines @@
       return new Future.delayed(delay, () {
         var h = collapse.getComputedStyle().height;
         // verify height
         expect(h, collapseHeight);
       });
     });
   });
 
   group('horizontal', () {
     IronCollapse collapse;
-    var delay = new Duration(milliseconds: 500);
+    var delay = 500;
     var width;
 
     setUp(() {
       collapse = fixture('horizontal');
     });
 
     test('opened attribute', () {
       expect(collapse.opened, true);
     });
 
     test('horizontal attribute', () {
       expect(collapse.horizontal, true);
     });
 
-    test('default opened width', () {
-      return new Future.delayed(delay, () {
-        // store height
-        width = collapse.getComputedStyle().width;
-        // verify height not 0px
-        expect(width, isNot('0px'));
-      });
+    test('default opened width', () async {
+      await wait(delay);
+      // store height
+      width = collapse.getComputedStyle().width;
+      // verify height not 0px
+      expect(width, isNot('0px'));
     });
 
-    test('set opened to false', () {
+    test('set opened to false', () async {
       collapse.opened = false;
-      return new Future.delayed(delay, () {
-        var w = collapse.getComputedStyle().width;
-        // verify height is 0px
-        expect(w, '0px');
-      });
+      await wait(delay);
+      var w = collapse.getComputedStyle().width;
+      // verify height is 0px
+      expect(w, '0px');
     });
 
-    test('set opened to true', () {
+    test('set opened to true', () async {
       collapse.opened = true;
-      return new Future.delayed(delay, () {
-        var w = collapse.getComputedStyle().width;
-        // verify height
-        expect(w, width);
-      });
+      await wait(delay);
+      var w = collapse.getComputedStyle().width;
+      // verify height
+      expect(w, width);
     });
   });
 }