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

net/socket/socks_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_SOCKS_CLIENT_SOCKET_H_
 #define NET_SOCKET_SOCKS_CLIENT_SOCKET_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 66 matching lines @@
     STATE_RESOLVE_HOST_COMPLETE,
     STATE_HANDSHAKE_WRITE,
     STATE_HANDSHAKE_WRITE_COMPLETE,
     STATE_HANDSHAKE_READ,
     STATE_HANDSHAKE_READ_COMPLETE,
     STATE_NONE,
   };
 
   void DoCallback(int result);
   void OnIOComplete(int result);
+  void OnReadWriteComplete(const CompletionCallback& callback, int result);
 
   int DoLoop(int last_io_result);
   int DoResolveHost();
   int DoResolveHostComplete(int result);
   int DoHandshakeRead();
   int DoHandshakeReadComplete(int result);
   int DoHandshakeWrite();
   int DoHandshakeWriteComplete(int result);
 
   const std::string BuildHandshakeWriteBuffer() const;
 
   // Stores the underlying socket.
   scoped_ptr<ClientSocketHandle> transport_;
 
   State next_state_;
 
-  // Stores the callback to the layer above, called on completing Connect().
+  // Stores the callbacks to the layer above, called on completing Connect().
   CompletionCallback user_callback_;
 
   // This IOBuffer is used by the class to read and write
   // SOCKS handshake data. The length contains the expected size to
   // read or write.
   scoped_refptr<IOBuffer> handshake_buf_;
 
   // While writing, this buffer stores the complete write handshake data.
   // While reading, it stores the handshake information received so far.
   std::string buffer_;
 
   // 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_;
 
+  // This becomes true when the socket is used to send or receive data.
+  bool was_ever_used_;
+
   // Used to resolve the hostname to which the SOCKS proxy will connect.
   SingleRequestHostResolver host_resolver_;
   AddressList addresses_;
   HostResolver::RequestInfo host_request_info_;
   RequestPriority priority_;
 
   BoundNetLog net_log_;
 
   DISALLOW_COPY_AND_ASSIGN(SOCKSClientSocket);
 };
 
 }  // namespace net
 
 #endif  // NET_SOCKET_SOCKS_CLIENT_SOCKET_H_