diff -r 000000000000 -r 6474c204b198 toolkit/mozapps/downloads/tests/unit/test_unspecified_arguments.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/mozapps/downloads/tests/unit/test_unspecified_arguments.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,25 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Make sure passing null and nothing to various variable-arg DownloadUtils
+ * methods provide the same result.
+ */
+
+let Cu = Components.utils;
+Cu.import("resource://gre/modules/DownloadUtils.jsm");
+
+function run_test()
+{
+  do_check_eq(DownloadUtils.getDownloadStatus(1000, null, null, null) + "",
+              DownloadUtils.getDownloadStatus(1000) + "");
+  do_check_eq(DownloadUtils.getDownloadStatus(1000, null, null) + "",
+              DownloadUtils.getDownloadStatus(1000, null) + "");
+
+  do_check_eq(DownloadUtils.getTransferTotal(1000, null) + "",
+              DownloadUtils.getTransferTotal(1000) + "");
+
+  do_check_eq(DownloadUtils.getTimeLeft(1000, null) + "",
+              DownloadUtils.getTimeLeft(1000) + "");
+}