When launching PNaCl helper nexes, explicitly disable IRT loading.

chrome/common/render_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.
 
 // Multiply-included file, no traditional include guard.
 #include <map>
 #include <set>
 #include <string>
 #include <vector>
 
@@ skipping 523 matching lines @@
 // A message for an external host.
 IPC_MESSAGE_ROUTED3(ChromeViewHostMsg_ForwardMessageToExternalHost,
                     std::string  /* message */,
                     std::string  /* origin */,
                     std::string  /* target */)
 
 // A renderer sends this to the browser process when it wants to start
 // a new instance of the Native Client process. The browser will launch
 // the process and return an IPC channel handle. This handle will only
 // be valid if the NaCl IPC proxy is enabled.
-IPC_SYNC_MESSAGE_CONTROL4_3(ChromeViewHostMsg_LaunchNaCl,
+IPC_SYNC_MESSAGE_CONTROL5_3(ChromeViewHostMsg_LaunchNaCl,
                             GURL /* manifest_url */,
                             int /* render_view_id */,
                             uint32 /* permission_bits */,
                             int /* socket count */,
+                            bool /* uses_irt */,
                             std::vector<nacl::FileDescriptor>
                                 /* imc channel handles */,
                             IPC::ChannelHandle /* ipc_channel_handle */,
                             int /* plugin_child_id */)
 
 // A renderer sends this to the browser process when it wants to
 // open a file for from the Pnacl component directory.
 IPC_SYNC_MESSAGE_CONTROL1_1(ChromeViewHostMsg_GetReadonlyPnaclFD,
                             std::string /* name of requested PNaCl file */,
                             IPC::PlatformFileForTransit /* output file */)
@@ skipping 153 matching lines @@
 // previous SetCookie message to be processed.
 IPC_SYNC_MESSAGE_ROUTED2_1(ChromeViewHostMsg_GetCookies,
                            GURL /* url */,
                            GURL /* first_party_for_cookies */,
                            std::string /* cookies */)
 
 // Provide the browser process with current renderer framerate.
 IPC_MESSAGE_CONTROL2(ChromeViewHostMsg_FPS,
                      int /* routing id */,
                      float /* frames per second */)