diff -r 000000000000 -r 6474c204b198 js/src/vm/PropertyKey.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/vm/PropertyKey.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,37 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* PropertyKey implementation details. */
+
+#include "js/PropertyKey.h"
+
+#include "jsatom.h"
+#include "jscntxt.h"
+
+#include "js/RootingAPI.h"
+#include "js/Value.h"
+#include "vm/String.h"
+
+using namespace js;
+
+bool
+JS::detail::ToPropertyKeySlow(JSContext *cx, HandleValue v, PropertyKey *key)
+{
+    MOZ_ASSERT_IF(v.isInt32(), v.toInt32() < 0);
+
+    RootedAtom atom(cx);
+    if (!ToAtom<CanGC>(cx, v))
+        return false;
+
+    uint32_t index;
+    if (atom->isIndex(&index)) {
+        *key = PropertyKey(index);
+        return true;
+    }
+
+    key->v.setString(atom->asPropertyName());
+    return true;
+}