diff -r 000000000000 -r 6474c204b198 dom/bindings/JSSlots.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/bindings/JSSlots.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,35 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
+/* 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/. */
+
+/**
+ * This file defines various reserved slot indices used by JavaScript
+ * reflections of DOM objects.
+ */
+#ifndef mozilla_dom_DOMSlots_h
+#define mozilla_dom_DOMSlots_h
+
+// We use slot 0 for holding the raw object.  This is safe for both
+// globals and non-globals.
+#define DOM_OBJECT_SLOT 0
+
+// The total number of slots non-proxy DOM objects use by default.
+// Specific objects may have more for storing cached values.
+#define DOM_INSTANCE_RESERVED_SLOTS 1
+
+// NOTE: This is baked into the Ion JIT as 0 in codegen for LGetDOMProperty and
+// LSetDOMProperty. Those constants need to be changed accordingly if this value
+// changes.
+#define DOM_PROTO_INSTANCE_CLASS_SLOT 0
+
+// Interface objects store a number of reserved slots equal to
+// DOM_INTERFACE_SLOTS_BASE + number of named constructors.
+#define DOM_INTERFACE_SLOTS_BASE 0
+
+// Interface prototype objects store a number of reserved slots equal to
+// DOM_INTERFACE_PROTO_SLOTS_BASE or DOM_INTERFACE_PROTO_SLOTS_BASE + 1 if a
+// slot for the unforgeable holder is needed.
+#define DOM_INTERFACE_PROTO_SLOTS_BASE (DOM_PROTO_INSTANCE_CLASS_SLOT + 1)
+
+#endif /* mozilla_dom_DOMSlots_h */