diff -r 000000000000 -r 6474c204b198 dom/base/nsISizeOfEventTarget.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/base/nsISizeOfEventTarget.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,40 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#ifndef nsISizeOfEventTarget_h___
+#define nsISizeOfEventTarget_h___
+
+#include "mozilla/MemoryReporting.h"
+#include "nsISupports.h"
+
+#define NS_ISIZEOFEVENTTARGET_IID \
+  {0xa1e08cb9, 0x5455, 0x4593, \
+    { 0xb4, 0x1f, 0x38, 0x7a, 0x85, 0x44, 0xd0, 0xb5 }}
+
+/**
+ * This class is much the same as nsISizeOf, but is specifically for measuring
+ * the contents of nsGlobalWindow::mEventTargetObjects.
+ *
+ * We don't use nsISizeOf because if we did, any object belonging to
+ * mEventTargetObjects that implements nsISizeOf would be measured, which we
+ * may not want (perhaps because the object is also measured elsewhere).
+ */
+class nsISizeOfEventTarget : public nsISupports
+{
+public:
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_ISIZEOFEVENTTARGET_IID)
+
+  /**
+   * Measures the size of the things pointed to by the object, plus the object
+   * itself.
+   */
+  virtual size_t
+    SizeOfEventTargetIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const = 0;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(nsISizeOfEventTarget, NS_ISIZEOFEVENTTARGET_IID)
+
+#endif /* nsISizeOfEventTarget_h___ */