Initial implementation of stashed message ports, content side

content/public/browser/message_port_delegate.h

Index: content/public/browser/message_port_delegate.h
diff --git a/content/public/browser/message_port_delegate.h b/content/public/browser/message_port_delegate.h
index 7c2de5bbde639534b86580c13f5e01eb696a6a1a..bbe6326fecc4d9b891cc5efe1575ca398a76d0ed 100644
--- a/content/public/browser/message_port_delegate.h
+++ b/content/public/browser/message_port_delegate.h
@@ -32,6 +32,11 @@ class CONTENT_EXPORT MessagePortDelegate {
       const MessagePortMessage& message,
       const std::vector<TransferredMessagePort>& sent_message_ports) = 0;
 
+  // Called when MessagePortService tried to send a message to a port, but
+  // instead added it to its queue because the port is currently configured to
+  // hold all its messages.
+  virtual void MessageWasHeld(int route_id) {}
+
   // Requests messages to the given route to be queued.
   virtual void SendMessagesAreQueued(int route_id) = 0;