diff -r 000000000000 -r 6474c204b198 addon-sdk/source/lib/sdk/base64.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/lib/sdk/base64.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,40 @@
+/* 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/. */
+
+"use strict";
+
+module.metadata = {
+  "stability": "unstable"
+};
+
+const { Cu } = require("chrome");
+
+// Passing an empty object as second argument to avoid scope's pollution
+const { atob, btoa } = Cu.import("resource://gre/modules/Services.jsm", {});
+
+function isUTF8(charset) {
+  let type = typeof charset;
+
+  if (type === "undefined")
+    return false;
+
+  if (type === "string" && charset.toLowerCase() === "utf-8")
+    return true;
+
+  throw new Error("The charset argument can be only 'utf-8'");
+}
+
+exports.decode = function (data, charset) {
+  if (isUTF8(charset))
+		return decodeURIComponent(escape(atob(data)))
+
+	return atob(data);
+}
+
+exports.encode = function (data, charset) {
+  if (isUTF8(charset))
+    return btoa(unescape(encodeURIComponent(data)))
+
+	return btoa(data);
+}