NaCl: Fix irt_ppapi.h to compile with -Wstrict-prototypes

ppapi/nacl_irt/public/irt_ppapi.h

 /*
  * 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.
  */
 
 #ifndef PPAPI_NACL_IRT_PUBLIC_IRT_PPAPI_H_
 #define PPAPI_NACL_IRT_PUBLIC_IRT_PPAPI_H_
 
 #include <stddef.h>
 
 #include "ppapi/c/ppp.h"
 
 struct PP_StartFunctions {
   int32_t (*PPP_InitializeModule)(PP_Module module_id,
                                   PPB_GetInterface get_browser_interface);
-  void (*PPP_ShutdownModule)();
+  void (*PPP_ShutdownModule)(void);
   const void* (*PPP_GetInterface)(const char* interface_name);
 };
 
 struct PP_ThreadFunctions {
   /*
    * This is a cut-down version of pthread_create()/pthread_join().
    * We omit thread creation attributes and the thread's return value.
    *
    * We use uintptr_t as the thread ID type because pthread_t is not
    * part of the stable ABI; a user thread library might choose an
    * arbitrary size for its own pthread_t.
    */
   int (*thread_create)(uintptr_t* tid,
                        void (*func)(void* thread_argument),
                        void* thread_argument);
   int (*thread_join)(uintptr_t tid);
 };
 
 #define NACL_IRT_PPAPIHOOK_v0_1 "nacl-irt-ppapihook-0.1"
 struct nacl_irt_ppapihook {
   int (*ppapi_start)(const struct PP_StartFunctions*);
   void (*ppapi_register_thread_creator)(const struct PP_ThreadFunctions*);
 };
 
 #endif  // PPAPI_NACL_IRT_PUBLIC_IRT_PPAPI_H_