Handle empty response to FTP QUIT message.

net/ftp/ftp_network_transaction.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_FTP_FTP_NETWORK_TRANSACTION_H_
 #define NET_FTP_FTP_NETWORK_TRANSACTION_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 230 matching lines @@
   bool use_epsv_;
 
   AuthCredentials credentials_;
 
   // Current directory on the remote server, as returned by last PWD command,
   // with any trailing slash removed.
   std::string current_remote_directory_;
 
   uint16_t data_connection_port_;
 
-  ClientSocketFactory* socket_factory_;
+  ClientSocketFactory* const socket_factory_;
 
   std::unique_ptr<StreamSocket> ctrl_socket_;
   std::unique_ptr<StreamSocket> data_socket_;
 
   State next_state_;
 
   // State to switch to after data connection is complete.
   State state_after_data_connect_complete_;
 };
 
 }  // namespace net
 
 #endif  // NET_FTP_FTP_NETWORK_TRANSACTION_H_