diff -r 000000000000 -r 6474c204b198 xpcom/base/nsInterfaceRequestorAgg.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/base/nsInterfaceRequestorAgg.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,36 @@
+/* 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 nsInterfaceRequestorAgg_h__
+#define nsInterfaceRequestorAgg_h__
+
+#include "nsError.h"
+
+class nsIEventTarget;
+class nsIInterfaceRequestor;
+
+/**
+ * This function returns an instance of nsIInterfaceRequestor that aggregates
+ * two nsIInterfaceRequestor instances.  Its GetInterface method queries
+ * aFirst for the requested interface and will query aSecond only if aFirst
+ * failed to supply the requested interface.  Both aFirst and aSecond may
+ * be null, and will be released on the main thread when the aggregator is
+ * destroyed.
+ */
+extern nsresult
+NS_NewInterfaceRequestorAggregation(nsIInterfaceRequestor  *aFirst,
+                                    nsIInterfaceRequestor  *aSecond,
+                                    nsIInterfaceRequestor **aResult);
+
+/**
+ * Like the previous method, but aFirst and aSecond will be released on the
+ * provided target thread.
+ */
+extern nsresult
+NS_NewInterfaceRequestorAggregation(nsIInterfaceRequestor  *aFirst,
+                                    nsIInterfaceRequestor  *aSecond,
+                                    nsIEventTarget         *aTarget,
+                                    nsIInterfaceRequestor **aResult);
+
+#endif // !defined( nsInterfaceRequestorAgg_h__ )