Cleaning up event constructors

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 bee3323b8866b1d7bc8748e877fb9b5fdea94e7c..271b4fc7ba10f58c7e7d700f2eae13c96f2d5c84 100644
--- a/tests/html/history_test.dart
+++ b/tests/html/history_test.dart
@@ -66,5 +66,12 @@ main() {
         expect(window.location.href.endsWith('foo=baz'), isTrue);
       }, expectation);
     });
+
+    test('hashchangeevent', () {
+      var event = new HashChangeEvent('change', oldUrl:'old', newUrl: 'new');
+      expect(event is HashChangeEvent, true);
+      expect(event.oldUrl, 'old');
+      expect(event.newUrl, 'new');
+    });
   });
 }