diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_8_5/extensions/regress-627984-6.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_8_5/extensions/regress-627984-6.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,15 @@
+// Any copyright is dedicated to the Public Domain.
+// http://creativecommons.org/licenses/publicdomain/
+
+// Bug 627984 description.
+var o = Array;
+o.p = function() {};
+o.watch('p', function() { }); 
+for(var x in o) { 
+    o[x]; 
+}
+delete o.p;
+o.p = function() {};
+assertEq(o.p, void 0);
+
+reportCompare(0, 0, 'ok');