Use sockets with unread data if they've never been used before.

net/socket/socks5_client_socket.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_SOCKET_SOCKS5_CLIENT_SOCKET_H_
 #define NET_SOCKET_SOCKS5_CLIENT_SOCKET_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 81 matching lines @@
 
   static const unsigned int kGreetReadHeaderSize;
   static const unsigned int kWriteHeaderSize;
   static const unsigned int kReadHeaderSize;
   static const uint8 kSOCKS5Version;
   static const uint8 kTunnelCommand;
   static const uint8 kNullByte;
 
   void DoCallback(int result);
   void OnIOComplete(int result);
+  void OnReadWriteComplete(const CompletionCallback& callback, int result);
 
   int DoLoop(int last_io_result);
   int DoHandshakeRead();
   int DoHandshakeReadComplete(int result);
   int DoHandshakeWrite();
   int DoHandshakeWriteComplete(int result);
   int DoGreetRead();
   int DoGreetReadComplete(int result);
   int DoGreetWrite();
   int DoGreetWriteComplete(int result);
@@ skipping 24 matching lines @@
   // This becomes true when the SOCKS handshake has completed and the
   // overlying connection is free to communicate.
   bool completed_handshake_;
 
   // These contain the bytes sent / received by the SOCKS handshake.
   size_t bytes_sent_;
   size_t bytes_received_;
 
   size_t read_header_size;
 
+  bool was_used_to_convey_data_;
+
   HostResolver::RequestInfo host_request_info_;
 
   BoundNetLog net_log_;
 
   DISALLOW_COPY_AND_ASSIGN(SOCKS5ClientSocket);
 };
 
 }  // namespace net
 
 #endif  // NET_SOCKET_SOCKS5_CLIENT_SOCKET_H_