ServiceWorker: Release a reference when it fails to dispatch ExtendableMessageEvent

content/browser/message_port_service.h

Index: content/browser/message_port_service.h
diff --git a/content/browser/message_port_service.h b/content/browser/message_port_service.h
index c3aeadb50a3ac6eaaea253eb5a5a1fd51ee49f32..b46a7fa36b1802e2a173081d5e4844de3560b083 100644
--- a/content/browser/message_port_service.h
+++ b/content/browser/message_port_service.h
@@ -67,6 +67,9 @@ class CONTENT_EXPORT MessagePortService {
   // clean up the port.
   void HoldMessages(int message_port_id);
 
+  // Returns true if messages for a message port are on hold.
+  bool AreMessagesHeld(int message_port_id);
+
   // Closes and cleans up the message port.
   void ClosePort(int message_port_id);