diff -r 000000000000 -r 6474c204b198 toolkit/forgetaboutsite/test/unit/head_forgetaboutsite.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/forgetaboutsite/test/unit/head_forgetaboutsite.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,43 @@
+/* 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/. */
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+
+var dirSvc = Cc["@mozilla.org/file/directory_service;1"].getService(Ci.nsIProperties);
+var profileDir = do_get_profile();
+
+/**
+ * Removes any files that could make our tests fail.
+ */
+function cleanUp()
+{
+  let files = [
+    "downloads.sqlite",
+    "places.sqlite",
+    "cookies.sqlite",
+    "signons.sqlite",
+    "permissions.sqlite"
+  ];
+
+  for (let i = 0; i < files.length; i++) {
+    let file = dirSvc.get("ProfD", Ci.nsIFile);
+    file.append(files[i]);
+    if (file.exists())
+      file.remove(false);
+  }
+}
+cleanUp();
+
+function oldDownloadManagerDisabled()
+{
+  try {
+    // This method throws an exception if the old Download Manager is disabled.
+    Services.downloads.activeDownloadCount;
+  } catch (ex) {
+    return true;
+  }
+  return false;
+}