Pepper: Stop using SRPC for irt_open_resource().

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 7802af30b1f7aa4711af327b0aa42c72c7ab3311..b3d2701f4aef7164283f6ce8af7920e353cc4d75 100644
--- a/ppapi/native_client/src/trusted/plugin/service_runtime.cc
+++ b/ppapi/native_client/src/trusted/plugin/service_runtime.cc
@@ -176,6 +176,10 @@ void PluginReverseInterface::OpenManifestEntry_MainThreadContinuation(
   UNREFERENCED_PARAMETER(err);
   // CallOnMainThread continuations always called with err == PP_OK.
 
+  // This method should only ever be called from the PNaCl translator, as the
+  // IRT is not available there.
+  CHECK(!service_runtime_->main_service_runtime());
+
   NaClLog(4, "Entered OpenManifestEntry_MainThreadContinuation\n");
 
   // Because p is owned by the callback of this invocation, so it is necessary