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..c84fdfcf5be5282f08a2cc8548d8443b16110514 100644
--- a/ppapi/native_client/src/trusted/plugin/service_runtime.cc
+++ b/ppapi/native_client/src/trusted/plugin/service_runtime.cc
@@ -712,6 +712,7 @@ bool ServiceRuntime::InitCommunication(nacl::DescWrapper* nacl_desc,
 bool ServiceRuntime::Start(nacl::DescWrapper* nacl_desc,
                            ErrorInfo* error_info,
                            const nacl::string& url,
+                           bool uses_irt,
                            bool uses_ppapi,
                            bool enable_ppapi_dev,
                            pp::CompletionCallback crash_cb) {
@@ -728,6 +729,7 @@ bool ServiceRuntime::Start(nacl::DescWrapper* nacl_desc,
   }
   bool started = tmp_subprocess->Start(plugin_->pp_instance(),
                                        url.c_str(),
+                                       uses_irt,
                                        uses_ppapi,
                                        enable_ppapi_dev);
   if (!started) {