Modified unittest to use new argument syntax.

tests/html/document_test.dart

Index: tests/html/document_test.dart
===================================================================
--- tests/html/document_test.dart	(revision 14156)
+++ tests/html/document_test.dart	(working copy)
@@ -6,11 +6,17 @@
 main() {
   useHtmlConfiguration();
 
+  var isElement = predicate((x) => x is Element, 'is an Element');
+  var isDivElement = predicate((x) => x is DivElement, 'is a DivElement');
+  var isAnchorElement =
+      predicate((x) => x is AnchorElement, 'is an AnchorElement');
+  var isUnknownElement = predicate((x) => x is Element, 'is UnknownElement');
+
   test('CreateElement', () {
     // FIXME: nifty way crashes, do it boring way.
-    Expect.isTrue(new Element.tag('span') is Element);
-    Expect.isTrue(new Element.tag('div') is DivElement);
-    Expect.isTrue(new Element.tag('a') is AnchorElement);
-    Expect.isTrue(new Element.tag('bad_name') is UnknownElement);
+    expect(new Element.tag('span'), isElement);
+    expect(new Element.tag('div'), isDivElement);
+    expect(new Element.tag('a'), isAnchorElement);
+    expect(new Element.tag('bad_name'), isUnknownElement);
   });
 }