diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_8_5/extensions/selfhosted-detecting-strict.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_8_5/extensions/selfhosted-detecting-strict.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,27 @@
+// Any copyright is dedicated to the Public Domain.
+// http://creativecommons.org/licenses/publicdomain/
+
+//-----------------------------------------------------------------------------
+var BUGNUMBER = 843004;
+var summary =
+  "Don't emit a strict warning for the undefined-property detection pattern in self-hosted code";
+
+print(BUGNUMBER + ": " + summary);
+
+/**************
+ * BEGIN TEST *
+ **************/
+
+options("strict", "werror");
+
+// Don't strict-warn (and throw, because of strict) when self-hosted code uses
+// detecting-safe undefined-property accesses (|options.weekday !== undefined|
+// and similar in ToDateTimeOptions, to be precise).
+new Date().toLocaleString("en-US", {});
+
+// If we get here, the test passed.
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);
+
+print("Tests complete");