diff -r 000000000000 -r 6474c204b198 dom/encoding/test/file_stringencoding.jsm
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/encoding/test/file_stringencoding.jsm	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,6 @@
+this.EXPORTED_SYMBOLS = ['checkFromJSM'];
+
+this.checkFromJSM = function checkFromJSM(is_op) {
+  is_op(new TextDecoder().encoding, "utf-8", "JSM should have TextDecoder");
+  is_op(new TextEncoder().encoding, "utf-8", "JSM should have TextEncoder");
+}