Modified unittest to use new argument syntax.

tests/html/datalistelement_test.dart

 // Copyright (c) 2012, 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('datalistelement_dataview_test');
 #import('../../pkg/unittest/unittest.dart');
 #import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 
 main() {
   useHtmlConfiguration();
 
+  var isDataListElement =
+      predicate((x) => x is DataListElement, 'is a DataListElement');
+
   var div;
 
   setUp(() {
       div = new DivElement();
       document.body.nodes.add(div);
       div.innerHTML = """
 <input id="input" list="browsers" />
 <datalist id="browsers">
   <option value="Chrome">
   <option value="Firefox">
   <option value="Internet Explorer">
   <option value="Opera">
   <option value="Safari">
 </datalist>
 """;
     });
 
   tearDown(() {
       document.body.nodes.removeLast();
     });
 
 
   test('is', () {
       var list = document.query('#browsers');
-      expect(list is DataListElement);
+      expect(list, isDataListElement);
   });
 
   test('list', () {
       var list = document.query('#browsers');
       var input = document.query('#input');
       expect(input.list, list);
   });
 
   test('options', () {
       var options = document.query('#browsers')
           .queryAll('option');  // Uses DataListElement.
       expect(options.length, 5);
   });
 
   test('create', () {
       var list = new DataListElement();
-      expect(list is DataListElement);
+      expect(list, isDataListElement);
     });
 }