diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/arrays/length-set-after-define-nonconfigurable.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/arrays/length-set-after-define-nonconfigurable.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,7 @@
+var arr = [1];
+Object.defineProperty(arr, 1, { value: undefined, configurable: false });
+
+// no particular reason for 9 -- just enough to trigger property-cache code,
+// maybe start JITting a little
+for (var y = 0; y < 9; y++)
+  arr.length = 1;