diff -r 000000000000 -r 6474c204b198 dom/interfaces/base/nsIContentURIGrouper.idl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/interfaces/base/nsIContentURIGrouper.idl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,23 @@
+/* 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/. */
+
+#include "nsIURI.idl"
+
+[scriptable, uuid(4bb38cb4-c3cb-4d17-9799-1b3132b39723)]
+interface nsIContentURIGrouper : nsISupports
+{
+    /**
+     * Determine the group to which the URI belongs.
+     *
+     * @param    aURI       the URI to group
+     *
+     * @returns  the group to which the URI belongs
+     */
+    AString group(in nsIURI aURI);
+};
+
+%{C++
+// The contractID for the generic implementation built in to xpcom.
+#define NS_HOSTNAME_GROUPER_SERVICE_CONTRACTID "@mozilla.org/content-pref/hostname-grouper;1"
+%}