diff -r 000000000000 -r 6474c204b198 toolkit/content/tests/widgets/head.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/content/tests/widgets/head.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,23 @@
+"use strict";
+
+function waitForCondition(condition, nextTest, errorMsg) {
+  var tries = 0;
+  var interval = setInterval(function() {
+    if (tries >= 30) {
+      ok(false, errorMsg);
+      moveOn();
+    }
+    var conditionPassed;
+    try {
+      conditionPassed = condition();
+    } catch (e) {
+      ok(false, e + "\n" + e.stack);
+      conditionPassed = false;
+    }
+    if (conditionPassed) {
+      moveOn();
+    }
+    tries++;
+  }, 100);
+  var moveOn = function() { clearInterval(interval); nextTest(); };
+}