diff -r 000000000000 -r 6474c204b198 addon-sdk/source/lib/sdk/loader/cuddlefish.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/lib/sdk/loader/cuddlefish.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,152 @@
+/* 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"
+};
+
+// This module is manually loaded by bootstrap.js in a sandbox and immediatly
+// put in module cache so that it is never loaded in any other way.
+
+/* Workarounds to include dependencies in the manifest
+require('chrome')                  // Otherwise CFX will complain about Components
+require('toolkit/loader')          // Otherwise CFX will stip out loader.js
+require('sdk/addon/runner')        // Otherwise CFX will stip out addon/runner.js
+require('sdk/system/xul-app')      // Otherwise CFX will stip out sdk/system/xul-app
+*/
+
+const { classes: Cc, Constructor: CC, interfaces: Ci, utils: Cu } = Components;
+
+// `loadSandbox` is exposed by bootstrap.js
+const loaderURI = module.uri.replace("sdk/loader/cuddlefish.js",
+                                     "toolkit/loader.js");
+const xulappURI = module.uri.replace("loader/cuddlefish.js",
+                                     "system/xul-app.js");
+// We need to keep a reference to the sandbox in order to unload it in
+// bootstrap.js
+
+const loaderSandbox = loadSandbox(loaderURI);
+const loaderModule = loaderSandbox.exports;
+
+const xulappSandbox = loadSandbox(xulappURI);
+const xulappModule = xulappSandbox.exports;
+
+const { override, load } = loaderModule;
+
+/**
+ * Ensure the current application satisfied the requirements specified in the
+ * module given. If not, an exception related to the incompatibility is
+ * returned; `null` otherwise.
+ *
+ * @param {Object} module
+ *  The module to check
+ * @returns {Error}
+ */
+function incompatibility(module) {
+  let { metadata, id } = module;
+
+  // if metadata or engines are not specified we assume compatibility is not
+  // an issue.
+  if (!metadata || !("engines" in metadata))
+    return null;
+
+  let { engines } = metadata;
+
+  if (engines === null || typeof(engines) !== "object")
+    return new Error("Malformed engines' property in metadata");
+
+  let applications = Object.keys(engines);
+
+  let versionRange;
+  applications.forEach(function(name) {
+    if (xulappModule.is(name)) {
+      versionRange = engines[name];
+      // Continue iteration. We want to ensure the module doesn't
+      // contain a typo in the applications' name or some unknown
+      // application - `is` function throws an exception in that case.
+    }
+  });
+
+  if (typeof(versionRange) === "string") {
+    if (xulappModule.satisfiesVersion(versionRange))
+      return null;
+
+    return new Error("Unsupported Application version: The module " + id +
+            " currently supports only version " + versionRange + " of " +
+            xulappModule.name + ".");
+  }
+
+  return new Error("Unsupported Application: The module " + id +
+            " currently supports only " + applications.join(", ") + ".")
+}
+
+function CuddlefishLoader(options) {
+  let { manifest } = options;
+
+  options = override(options, {
+    // Put `api-utils/loader` and `api-utils/cuddlefish` loaded as JSM to module
+    // cache to avoid subsequent loads via `require`.
+    modules: override({
+      'toolkit/loader': loaderModule,
+      'sdk/loader/cuddlefish': exports,
+      'sdk/system/xul-app': xulappModule
+    }, options.modules),
+    resolve: function resolve(id, requirer) {
+      let entry = requirer && requirer in manifest && manifest[requirer];
+      let uri = null;
+
+      // If manifest entry for this requirement is present we follow manifest.
+      // Note: Standard library modules like 'panel' will be present in
+      // manifest unless they were moved to platform.
+      if (entry) {
+        let requirement = entry.requirements[id];
+        // If requirer entry is in manifest and it's requirement is not, than
+        // it has no authority to load since linker was not able to find it.
+        if (!requirement)
+          throw Error('Module: ' + requirer + ' has no authority to load: '
+                      + id, requirer);
+
+        uri = requirement;
+      } else {
+        // If requirer is off manifest than it's a system module and we allow it
+        // to go off manifest by resolving a relative path.
+        uri = loaderModule.resolve(id, requirer);
+      }
+      return uri;
+    },
+    load: function(loader, module) {
+      let result;
+      let error;
+
+      // In order to get the module's metadata, we need to load the module.
+      // if an exception is raised here, it could be that is due to application
+      // incompatibility. Therefore the exception is stored, and thrown again
+      // only if the module seems be compatible with the application currently
+      // running. Otherwise the incompatibility message takes the precedence.
+      try {
+        result = load(loader, module);
+      }
+      catch (e) {
+        error = e;
+      }
+
+      error = incompatibility(module) || error;
+
+      if (error)
+        throw error;
+
+      return result;
+    }
+  });
+
+  let loader = loaderModule.Loader(options);
+  // Hack to allow loading from `toolkit/loader`.
+  loader.modules[loaderURI] = loaderSandbox;
+  return loader;
+}
+
+exports = override(loaderModule, {
+  Loader: CuddlefishLoader
+});