Add an XPC implementation of sandbox::MessageServer.

sandbox/mac/xpc_private_stubs.sig

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file contains declarations of private XPC functions. This file is
 // used for both forward declarations of private symbols and to use with
 // tools/generate_stubs for creating a dynamic library loader.
 
 // Dictionary manipulation.
-void xpc_dictionary_set_mach_send(xpc_object_t dict, const char* name, mach_port_t port);
+void xpc_dictionary_set_mach_send(xpc_object_t dictionary, const char* name, mach_port_t port);
+void xpc_dictionary_get_audit_token(xpc_object_t dictionary, audit_token_t* token);
 
 // Pipe methods.
 xpc_pipe_t xpc_pipe_create_from_port(mach_port_t port, int flags);
 int xpc_pipe_receive(mach_port_t port, xpc_object_t* message);
 int xpc_pipe_routine(xpc_pipe_t pipe, xpc_object_t request, xpc_object_t* reply);
 int xpc_pipe_routine_reply(xpc_object_t reply);
+int xpc_pipe_simpleroutine(xpc_pipe_t pipe, xpc_object_t message);
 int xpc_pipe_routine_forward(xpc_pipe_t forward_to, xpc_object_t request);