When launching PNaCl helper nexes, explicitly disable IRT loading.

ppapi/api/private/ppb_nacl_private.idl

 /* Copyright (c) 2012 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 NaCl private interfaces. */
 
 #inline c
 #include "ppapi/c/private/pp_file_handle.h"
 #endinl
@@ skipping 26 matching lines @@
 
 /* PPB_NaCl_Private */
 interface PPB_NaCl_Private {
   /* Launches NaCl's sel_ldr process.  Returns PP_NACL_OK on success and
    * writes a nacl::Handle to imc_handle. Returns PP_NACL_FAILED on failure.
    * The |enable_ppapi_dev| parameter controls whether GetInterface
    * returns 'Dev' interfaces to the NaCl plugin.  The |uses_ppapi| flag
    * indicates that the nexe run by sel_ldr will use the PPAPI APIs.
    * This implies that LaunchSelLdr is run from the main thread.  If a nexe
    * does not need PPAPI, then it can run off the main thread.
+   * The |uses_irt| flag indicates whether the IRT should be loaded in this
+   * NaCl process.  This is true for ABI stable nexes.
    */
   PP_NaClResult LaunchSelLdr([in] PP_Instance instance,
                              [in] str_t alleged_url,
+                             [in] PP_Bool uses_irt,
                              [in] PP_Bool uses_ppapi,
                              [in] PP_Bool enable_ppapi_dev,
                              [out] mem_t imc_handle);
 
   /* This function starts the IPC proxy so the nexe can communicate with the
    * browser. Returns PP_NACL_OK on success, otherwise a result code indicating
    * the failure. PP_NACL_FAILED is returned if LaunchSelLdr wasn't called with
    * the instance. PP_NACL_ERROR_MODULE is returned if the module can't be
    * initialized. PP_NACL_ERROR_INSTANCE is returned if the instance can't be
    * initialized. PP_NACL_USE_SRPC is returned if the plugin should use SRPC.
@@ skipping 45 matching lines @@
   PP_Bool IsOffTheRecord();
 
   /* Return true if PNaCl is turned on.
    */
   PP_Bool IsPnaclEnabled();
 
   /* Display a UI message to the user. */
   PP_NaClResult ReportNaClError([in] PP_Instance instance,
                                 [in] PP_NaClError message_id);
 };