Implement the close() API for Message ports

content/public/browser/message_port_provider.h

Index: content/public/browser/message_port_provider.h
diff --git a/content/public/browser/message_port_provider.h b/content/public/browser/message_port_provider.h
index 1042399fdb4311c4d375458e4b65c34ebf265290..8a725de00b59e8ded8c0248fe5da45cdb75912f8 100644
--- a/content/public/browser/message_port_provider.h
+++ b/content/public/browser/message_port_provider.h
@@ -47,6 +47,9 @@ class CONTENT_EXPORT MessagePortProvider {
                                 const base::string16& data,
                                 const std::vector<int>& sent_ports);
 
+  // Close the message port. Should be called on IO thread.
+  static void ClosePort(int message_port_id);
+
   // Cleanup the message ports that belong to the closing delegate.
   static void OnMessagePortDelegateClosing(MessagePortDelegate * delegate);