diff -r 000000000000 -r 6474c204b198 browser/components/translation/LanguageDetector.jsm
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/translation/LanguageDetector.jsm	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,55 @@
+/* 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";
+
+this.EXPORTED_SYMBOLS = ["LanguageDetector"];
+
+Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "Promise",
+                                  "resource://gre/modules/Promise.jsm");
+
+const WORKER_URL = "resource:///modules/translation/cld-worker.js";
+
+let detectionQueue = [];
+
+let workerReady = false;
+let pendingStrings = [];
+
+XPCOMUtils.defineLazyGetter(this, "worker", () => {
+  let worker = new Worker(WORKER_URL);
+  worker.onmessage = function(aMsg) {
+    if (aMsg.data == "ready") {
+      workerReady = true;
+      for (let string of pendingStrings)
+        worker.postMessage(string);
+      pendingStrings = [];
+    }
+    else
+      detectionQueue.shift().resolve(aMsg.data);
+  }
+  return worker;
+});
+
+this.LanguageDetector = {
+  /**
+   * Detect the language of a given string
+   *
+   * @returns {Promise}
+   * @resolves When detection is finished, with a object containing
+   * these fields:
+   *  - 'language' (string with a language code)
+   *  - 'confident' (boolean).
+   */
+  detectLanguage: function(aString) {
+    let deferred = Promise.defer();
+    detectionQueue.push(deferred);
+    if (worker && workerReady)
+      worker.postMessage(aString);
+    else
+      pendingStrings.push(aString);
+    return deferred.promise;
+  }
+};