When launching PNaCl helper nexes, explicitly disable IRT loading.

ppapi/native_client/src/trusted/plugin/service_runtime.cc

Index: ppapi/native_client/src/trusted/plugin/service_runtime.cc
diff --git a/ppapi/native_client/src/trusted/plugin/service_runtime.cc b/ppapi/native_client/src/trusted/plugin/service_runtime.cc
index c5b9f7e04ad774919fb4997d71f1c9579a853c66..201e66c73999ec9d3308a539ef2bad2ab8c2946b 100644
--- a/ppapi/native_client/src/trusted/plugin/service_runtime.cc
+++ b/ppapi/native_client/src/trusted/plugin/service_runtime.cc
@@ -714,6 +714,7 @@ bool ServiceRuntime::Start(nacl::DescWrapper* nacl_desc,
                            const nacl::string& url,
                            bool uses_ppapi,
                            bool enable_ppapi_dev,
+                           bool uses_irt,
                            pp::CompletionCallback crash_cb) {
   PLUGIN_PRINTF(("ServiceRuntime::Start (nacl_desc=%p)\n",
                  reinterpret_cast<void*>(nacl_desc)));
@@ -729,7 +730,8 @@ bool ServiceRuntime::Start(nacl::DescWrapper* nacl_desc,
   bool started = tmp_subprocess->Start(plugin_->pp_instance(),
                                        url.c_str(),
                                        uses_ppapi,
-                                       enable_ppapi_dev);
+                                       enable_ppapi_dev,
+                                       uses_irt);
   if (!started) {
     PLUGIN_PRINTF(("ServiceRuntime::Start (start failed)\n"));
     error_info->SetReport(ERROR_SEL_LDR_LAUNCH,