Modified unittest to use new argument syntax.

tests/html/hidden_dom_2_test.dart

 #library('HiddenDom2Test');
 #import('../../pkg/unittest/unittest.dart');
 #import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 
 // Test that the dart:html API does not leak native jsdom methods:
 //   appendChild operation.
 
 main() {
   useHtmlConfiguration();
 
   test('test1', () {
     document.body.elements.add(new Element.html(r'''
 <div id='div1'>
 Hello World!
 </div>'''));
     Element e = document.query('#div1');
     Element e2 = new Element.html(r"<div id='xx'>XX</div>");
-    Expect.isTrue(e != null);
+    expect(e, isNotNull);
 
     checkNoSuchMethod(() { confuse(e).appendChild(e2); });
 
   });
 }
 
 class Decoy {
   void appendChild(x) { throw 'dead code'; }
 }
 
 confuse(x) => opaqueTrue() ? x : (opaqueTrue() ? new Object() : new Decoy());
 
 /** Returns [:true:], but in a way that confuses the compiler. */
 opaqueTrue() => true;  // Expand as needed.
 
 checkNoSuchMethod(action()) {
   var ex = null;
   bool threw = false;
   try {
     action();
   } catch (e) {
     threw = true;
     ex = e;
   }
   if (!threw)
-    Expect.fail('Action should have thrown exception');
+    expect(false, isTrue, reason: 'Action should have thrown exception');
 
-  Expect.isTrue(ex is NoSuchMethodError, 'ex is NoSuchMethodError');
+  expect(ex, isNoSuchMethodError);
 }