Fixing tests after event constructor change.

tests/html/history_test.dart

Index: tests/html/history_test.dart
diff --git a/tests/html/history_test.dart b/tests/html/history_test.dart
index 271b4fc7ba10f58c7e7d700f2eae13c96f2d5c84..211b950ee742922e44ba5913245703c05a132ff2 100644
--- a/tests/html/history_test.dart
+++ b/tests/html/history_test.dart
@@ -68,10 +68,12 @@ main() {
     });
 
     test('hashchangeevent', () {
-      var event = new HashChangeEvent('change', oldUrl:'old', newUrl: 'new');
-      expect(event is HashChangeEvent, true);
-      expect(event.oldUrl, 'old');
-      expect(event.newUrl, 'new');
+      expect(() {
+        var event = new HashChangeEvent('change', oldUrl:'old', newUrl: 'new');
+        expect(event is HashChangeEvent, true);
+        expect(event.oldUrl, 'old');
+        expect(event.newUrl, 'new');
+      }, expectation);
     });
   });
 }