diff -r 000000000000 -r 6474c204b198 toolkit/mozapps/extensions/internal/SpellCheckDictionaryBootstrap.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/mozapps/extensions/internal/SpellCheckDictionaryBootstrap.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/. */
+
+var hunspell, dir;
+
+function startup(data) {
+  hunspell = Components.classes["@mozilla.org/spellchecker/engine;1"]
+                       .getService(Components.interfaces.mozISpellCheckingEngine);
+  dir = data.installPath.clone();
+  dir.append("dictionaries");
+  hunspell.addDirectory(dir);
+}
+
+function shutdown() {
+  hunspell.removeDirectory(dir);
+}