When launching PNaCl helper nexes, explicitly disable IRT loading.

chrome/common/nacl_messages.h

 // 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.
 
 // Defines messages between the browser and NaCl process.
 
 // Multiply-included message file, no traditional include guard.
 #include "base/process.h"
 #include "chrome/common/nacl_types.h"
 #include "ipc/ipc_channel_handle.h"
 #include "ipc/ipc_message_macros.h"
 
 #define IPC_MESSAGE_START NaClMsgStart
 
 IPC_STRUCT_TRAITS_BEGIN(nacl::NaClStartParams)
   IPC_STRUCT_TRAITS_MEMBER(handles)
   IPC_STRUCT_TRAITS_MEMBER(debug_stub_server_bound_socket)
   IPC_STRUCT_TRAITS_MEMBER(validation_cache_enabled)
   IPC_STRUCT_TRAITS_MEMBER(validation_cache_key)
   IPC_STRUCT_TRAITS_MEMBER(version)
   IPC_STRUCT_TRAITS_MEMBER(enable_exception_handling)
   IPC_STRUCT_TRAITS_MEMBER(enable_debug_stub)
   IPC_STRUCT_TRAITS_MEMBER(enable_ipc_proxy)
+  IPC_STRUCT_TRAITS_MEMBER(uses_irt)
 IPC_STRUCT_TRAITS_END()
 
 //-----------------------------------------------------------------------------
 // NaClProcess messages
 // These are messages sent between the browser and the NaCl process.
 // Tells the NaCl process to start.
 IPC_MESSAGE_CONTROL1(NaClProcessMsg_Start,
                      nacl::NaClStartParams /* params */)
 
 #if defined(OS_WIN)
@@ skipping 39 matching lines @@
 
 // Used by the NaCl process to add a validation signature to the validation
 // database in the browser.
 IPC_MESSAGE_CONTROL1(NaClProcessMsg_SetKnownToValidate,
                      std::string /* A validation signature */)
 
 // Notify the browser process that the server side of the PPAPI channel was
 // created successfully.
 IPC_MESSAGE_CONTROL1(NaClProcessHostMsg_PpapiChannelCreated,
                      IPC::ChannelHandle /* channel_handle */)
-