diff -r 000000000000 -r 6474c204b198 toolkit/devtools/apps/Simulator.jsm
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/devtools/apps/Simulator.jsm	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,33 @@
+/* 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";
+
+Components.utils.import("resource://gre/modules/devtools/event-emitter.js");
+
+const EXPORTED_SYMBOLS = ["Simulator"];
+
+const Simulator = {
+  _simulators: {},
+
+  register: function (version, simulator) {
+    this._simulators[version] = simulator;
+    this.emit("register");
+  },
+
+  unregister: function (version) {
+    delete this._simulators[version];
+    this.emit("unregister");
+  },
+
+  availableVersions: function () {
+    return Object.keys(this._simulators).sort();
+  },
+
+  getByVersion: function (version) {
+    return this._simulators[version];
+  }
+};
+
+EventEmitter.decorate(Simulator);