diff -r 000000000000 -r 6474c204b198 layout/tools/layout-debug/layoutdebug-prefs.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/tools/layout-debug/layoutdebug-prefs.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,5 @@
+/* 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/. */
+
+pref("toolkit.defaultChromeURI", "chrome://layoutdebug/content/layoutdebug.xul");