[Extensions] Make port creation synchronous in unload handlers

chrome/browser/renderer_host/chrome_extension_message_filter.h

Index: chrome/browser/renderer_host/chrome_extension_message_filter.h
diff --git a/chrome/browser/renderer_host/chrome_extension_message_filter.h b/chrome/browser/renderer_host/chrome_extension_message_filter.h
index 0ad57f3de98c4c8e67a553b282f1213d16fe8518..ff79393b4f37cf748851ddaaf8ae5962e8011cae 100644
--- a/chrome/browser/renderer_host/chrome_extension_message_filter.h
+++ b/chrome/browser/renderer_host/chrome_extension_message_filter.h
@@ -58,6 +58,12 @@ class ChromeExtensionMessageFilter : public content::BrowserMessageFilter,
                                 const std::string& channel_name,
                                 bool include_tls_channel_id,
                                 int request_id);
+  void OnOpenChannelToExtensionSync(
+      int routing_id,
+      const ExtensionMsg_ExternalConnectionInfo& info,
+      const std::string& channel_name,
+      bool include_tls_channel_id,
+      int* port_id);
   void OpenChannelToExtensionOnUIThread(
       int source_process_id,
       int source_routing_id,