Allow non-primitive-value dictionaries to be passed to constructors for html

tests/html/notifications_test.dart

Index: tests/html/notifications_test.dart
diff --git a/tests/html/notifications_test.dart b/tests/html/notifications_test.dart
index 796680f72114c43edee69a3c44fe40f07d257c18..eb1a9a378673f5cc9f8daac77d242bec5441710a 100644
--- a/tests/html/notifications_test.dart
+++ b/tests/html/notifications_test.dart
@@ -28,6 +28,12 @@ main() {
           expect(e.name, DomException.SECURITY);
         }
       });
+
+      test('construct notification', () {
+        var note = new Notification('this is a notification');
+        var note2 = new Notification('another notificiation',
+          {'option1': 'foo'});
+      });
     }
   });
 }