diff -r 000000000000 -r 6474c204b198 dom/devicestorage/test/devicestorage_common.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/devicestorage/test/devicestorage_common.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,79 @@
+/**
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+var oldVal = false;
+  
+Object.defineProperty(Array.prototype, "remove", {
+  enumerable: false,
+  configurable: false,
+  writable: false,
+  value: function(from, to) {
+    // Array Remove - By John Resig (MIT Licensed)
+    var rest = this.slice((to || from) + 1 || this.length);
+    this.length = from < 0 ? this.length + from : from;
+    return this.push.apply(this, rest);
+  }
+});
+
+function devicestorage_setup() {
+
+  // ensure that the directory we are writing into is empty
+  try {
+    const Cc = SpecialPowers.Cc;
+    const Ci = SpecialPowers.Ci;
+    var directoryService = Cc["@mozilla.org/file/directory_service;1"].getService(Ci.nsIProperties);
+    var f = directoryService.get("TmpD", Ci.nsIFile);
+    f.appendRelativePath("device-storage-testing");
+    f.remove(true);
+  } catch(e) {}
+
+  SimpleTest.waitForExplicitFinish();
+  if (SpecialPowers.isMainProcess()) {
+    try {
+      oldVal = SpecialPowers.getBoolPref("device.storage.enabled");
+    } catch(e) {}
+    SpecialPowers.setBoolPref("device.storage.enabled", true);
+    SpecialPowers.setBoolPref("device.storage.testing", true);
+    SpecialPowers.setBoolPref("device.storage.prompt.testing", true);
+  }
+}
+
+function devicestorage_cleanup() {
+  if (SpecialPowers.isMainProcess()) {
+    SpecialPowers.setBoolPref("device.storage.enabled", oldVal);
+    SpecialPowers.setBoolPref("device.storage.testing", false);
+    SpecialPowers.setBoolPref("device.storage.prompt.testing", false);
+  }
+  SimpleTest.finish();
+}
+
+function getRandomBuffer() {
+  var size = 1024;
+  var buffer = new ArrayBuffer(size);
+  var view = new Uint8Array(buffer);
+  for (var i = 0; i < size; i++) {
+    view[i] = parseInt(Math.random() * 255);
+  }
+  return buffer;
+}
+
+function createRandomBlob(mime) {
+  return blob = new Blob([getRandomBuffer()], {type: mime});
+}
+
+function randomFilename(l) {
+  var set = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZ";
+  var result = "";
+  for (var i=0; i<l; i++) {
+    var r = Math.floor(set.length * Math.random());
+    result += set.substring(r, r + 1);
+  }
+  return result;
+}
+
+function reportErrorAndQuit(e) {
+  ok(false, "handleError was called : " + e.target.error.name);
+  devicestorage_cleanup();
+}