Modified unittest to use new argument syntax.

tests/html/xsltprocessor_test.dart

 #library('XSLTProcessorTest');
 #import('../../pkg/unittest/unittest.dart');
 #import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 
 main() {
 
   useHtmlConfiguration();
 
+  var isXSLTProcessor =
+      predicate((x) => x is XSLTProcessor, 'is an XSLTProcessor');
+
   test('constructorTest', () {
       var processor = new XSLTProcessor();
-      Expect.isTrue(processor != null);
-      Expect.isTrue(processor is XSLTProcessor);
+      expect(processor, isNotNull);
+      expect(processor, isXSLTProcessor);
     });
 }