diff -r 000000000000 -r 6474c204b198 dom/settings/SettingsQueue.jsm
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/settings/SettingsQueue.jsm	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,30 @@
+/* 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/. */
+
+this.EXPORTED_SYMBOLS = ["Queue"];
+
+this.Queue = function Queue() {
+  this._queue = [];
+  this._index = 0;
+}
+
+Queue.prototype = {
+  getLength: function() { return (this._queue.length - this._index); },
+
+  isEmpty: function() { return (this._queue.length == 0); },
+
+  enqueue: function(item) { this._queue.push(item); },
+
+  dequeue: function() {
+    if(this.isEmpty())
+      return undefined;
+
+    var item = this._queue[this._index];
+    if (++this._index * 2 >= this._queue.length){
+      this._queue  = this._queue.slice(this._index);
+      this._index = 0;
+    }
+    return item;
+  }
+}