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

src/trusted/service_runtime/sel_main_chrome.c

Index: src/trusted/service_runtime/sel_main_chrome.c
diff --git a/src/trusted/service_runtime/sel_main_chrome.c b/src/trusted/service_runtime/sel_main_chrome.c
index 9c38628551823f557a58b4ac3c123a62430df51f..39665612498a8c15b80dc1320fa2608eaf0734b8 100644
--- a/src/trusted/service_runtime/sel_main_chrome.c
+++ b/src/trusted/service_runtime/sel_main_chrome.c
@@ -76,6 +76,7 @@ struct NaClChromeMainArgs *NaClChromeMainArgsCreate(void) {
 #if NACL_LINUX || NACL_OSX
   args->debug_stub_server_bound_socket_fd = NACL_INVALID_SOCKET;
 #endif
+  args->debug_stub_server_port_selected_handler_func = NULL;
   args->create_memory_object_func = NULL;
   args->validation_cache = NULL;
 #if NACL_WINDOWS
@@ -338,6 +339,9 @@ void NaClChromeMainStartApp(struct NaClApp *nap,
     if (!NaClDebugInit(nap)) {
       goto done;
     }
+    if (NULL != args->debug_stub_server_port_selected_handler_func) {
+      args->debug_stub_server_port_selected_handler_func(nap->debug_stub_port);
+    }
   }
 
   free(args);