Partly change IRT load-skipping to be explicit.

src/trusted/service_runtime/sel_main_chrome.h

 /*
  * Copyright (c) 2012 The Native Client 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 NATIVE_CLIENT_SRC_TRUSTED_SERVICE_RUNTIME_SEL_MAIN_CHROME_H_
 #define NATIVE_CLIENT_SRC_TRUSTED_SERVICE_RUNTIME_SEL_MAIN_CHROME_H_ 1
 
 #include "native_client/src/include/nacl_base.h"
@@ skipping 16 matching lines @@
 struct NaClChromeMainArgs {
   /*
    * Handle for bootstrapping a NaCl IMC connection to the trusted
    * PPAPI plugin.  Required.
    */
   NaClHandle imc_bootstrap_handle;
 
   /*
    * File descriptor for the NaCl integrated runtime (IRT) library.
    * Note that this is a file descriptor even on Windows (where file
-   * descriptors are emulated by the C runtime library).  Required.
+   * descriptors are emulated by the C runtime library).
+   * Optional; may be -1.  Optional when loading nexes that don't follow
+   * NaCl's stable ABI, such as the PNaCl translator.
    */
   int irt_fd;
 
   /*
    * Descriptor to provide to untrusted code as descriptor number
    * NACL_CHROME_INITIAL_IPC_DESC.  For use by the Chrome-IPC-based
    * PPAPI proxy.  Optional; may be NULL.
    */
   struct NaClDesc *initial_ipc_desc;
 
@@ skipping 61 matching lines @@
 /* Create a new args struct containing default values. */
 struct NaClChromeMainArgs *NaClChromeMainArgsCreate(void);
 
 /* Launch NaCl. */
 void NaClChromeMainStart(struct NaClChromeMainArgs *args);
 
 
 EXTERN_C_END
 
 #endif