diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_8/extensions/for-in.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_8/extensions/for-in.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,55 @@
+// |reftest| skip
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ * Contributor: Jason Orendorff
+ */
+
+//-----------------------------------------------------------------------------
+
+var summary = "Contention among threads enumerating properties";
+// Adapted from mozilla/js/src/xpconnect/tests/js/old/threads.js
+
+printStatus (summary);
+
+var LOOP_COUNT = 1000;
+var THREAD_COUNT = 10;
+
+var foo;
+var bar;
+
+function makeWorkerFn(id) {
+  return function() {
+    foo = id + 1;
+    bar[id] = {p: 0};
+    var n, m;
+    for (n in bar) {
+      for (m in bar[n]) {}
+    }
+    for (n in parent({})) {}
+  };
+}
+
+function range(n) {
+  for (let i = 0; i < n; i++)
+    yield i;
+}
+
+var expect;
+var actual;
+
+expect = actual = 'No crash';
+if (typeof scatter == 'undefined') {
+  print('Test skipped. scatter not defined.');
+} else if (typeof parent === "undefined") {
+  print('Test skipped, no parent() function.');
+} else {
+  for (let i = 0; i < LOOP_COUNT; i++) {
+    foo = 0;
+    bar = new Array(THREAD_COUNT);
+    scatter([makeWorkerFn(j) for (j in range(THREAD_COUNT))]);
+  }
+}
+
+reportCompare(expect, actual, summary);