When launching PNaCl helper nexes, explicitly disable IRT loading.

chrome/browser/nacl_host/nacl_process_host.cc

Index: chrome/browser/nacl_host/nacl_process_host.cc
diff --git a/chrome/browser/nacl_host/nacl_process_host.cc b/chrome/browser/nacl_host/nacl_process_host.cc
index 3119c1b1dd9b1bce1b6c89aeabf41b6821d4f005..98fac1414ef61375b97c40ad5feecc9cba866b81 100644
--- a/chrome/browser/nacl_host/nacl_process_host.cc
+++ b/chrome/browser/nacl_host/nacl_process_host.cc
@@ -144,7 +144,8 @@ bool NaClProcessHost::PluginListener::OnMessageReceived(
 NaClProcessHost::NaClProcessHost(const GURL& manifest_url,
                                  int render_view_id,
                                  uint32 permission_bits,
-                                 bool off_the_record)
+                                 bool off_the_record,
+                                 bool uses_irt)
     : manifest_url_(manifest_url),
       permissions_(GetNaClPermissions(permission_bits)),
 #if defined(OS_WIN)
@@ -162,6 +163,7 @@ NaClProcessHost::NaClProcessHost(const GURL& manifest_url,
       enable_debug_stub_(false),
       off_the_record_(off_the_record),
       enable_ipc_proxy_(false),
+      uses_irt_(uses_irt),
       ALLOW_THIS_IN_INITIALIZER_LIST(ipc_plugin_listener_(this)),
       render_view_id_(render_view_id) {
   process_.reset(content::BrowserChildProcessHost::Create(
@@ -712,6 +714,7 @@ bool NaClProcessHost::StartNaClExecution() {
   params.enable_debug_stub = enable_debug_stub_ &&
       NaClBrowser::GetInstance()->URLMatchesDebugPatterns(manifest_url_);
   params.enable_ipc_proxy = enable_ipc_proxy_;
+  params.uses_irt = uses_irt_;
 
   base::PlatformFile irt_file = nacl_browser->IrtFile();
   CHECK_NE(irt_file, base::kInvalidPlatformFileValue);