Provide chrome the option of learning the debug stub port chosen by nacl.

src/trusted/service_runtime/sel_ldr.h

Index: src/trusted/service_runtime/sel_ldr.h
diff --git a/src/trusted/service_runtime/sel_ldr.h b/src/trusted/service_runtime/sel_ldr.h
index 49147e9b4db4737914bda71f5ad71747c696f26a..f18a707bf568aff78360bcfffc0d571331ebf616 100644
--- a/src/trusted/service_runtime/sel_ldr.h
+++ b/src/trusted/service_runtime/sel_ldr.h
@@ -391,6 +391,7 @@ struct NaClApp {
   struct DynArray           desc_tbl;  /* NaClDesc pointers */
 
   const struct NaClDebugCallbacks *debug_stub_callbacks;
+  uint16_t                        debug_stub_port;
   struct NaClDesc                 *main_nexe_desc;
 
   struct NaClMutex          exception_mu;