diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/indexed-iteration.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/indexed-iteration.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,20 @@
+
+// Don't use NativeIterator cache for objects with dense elements.
+
+function bar(a) {
+  var n = 0;
+  for (var b in a) { n++; }
+  return n;
+}
+
+function foo() {
+  var x = {a:0,b:1};
+  var y = {a:0,b:1};
+  y[0] = 2;
+  y[1] = 3;
+  for (var i = 0; i < 10; i++) {
+    assertEq(bar(x), 2);
+    assertEq(bar(y), 4);
+  }
+}
+foo();