Modified unittest to use new argument syntax.

tests/html/shadowroot_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('ShadowRootTest');
 #import('../../pkg/unittest/unittest.dart');
 #import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 
 main() {
   useHtmlConfiguration();
 
+  var isShadowRoot =
+      predicate((x) => x is ShadowRoot, 'is a ShadowRoot');
+
   test('ShadowRoot supported', () {
     var isSupported = ShadowRoot.supported;
 
     // If it's supported, then it should work. Otherwise should fail.
     if (isSupported) {
       var shadowRoot = new ShadowRoot(new DivElement());
-      expect(shadowRoot is ShadowRoot);
+      expect(shadowRoot, isShadowRoot);
     } else {
       expect(() => new ShadowRoot(new DivElement()), throws);
     }
   });
 }