diff -r 000000000000 -r 6474c204b198 toolkit/components/downloads/test/unit/test_bug_384744.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/downloads/test/unit/test_bug_384744.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,17 @@
+/* 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/. */
+
+// This file tests Bug 384744 - or specifically that createInstance won't cause
+// a failure with the download manager.  The old practice was bad because if
+// someone called createInstance before anyone called getService, getService
+// would fail, and we would have a non-functional download manager.
+
+function run_test()
+{
+  var dmci = Cc["@mozilla.org/download-manager;1"].
+             createInstance(Ci.nsIDownloadManager);
+  var dmgs = Cc["@mozilla.org/download-manager;1"].
+             getService(Ci.nsIDownloadManager);
+  do_check_eq(dmci, dmgs);
+}