Add a new GetNegotiatedProtocol method to StreamSocket and implement in all subclasses.

net/socket/tcp_client_socket_libevent.cc

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
 #include "net/socket/tcp_client_socket.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <netdb.h>
 #include <sys/socket.h>
 #include <netinet/tcp.h>
@@ skipping 714 matching lines @@
 }
 
 int64 TCPClientSocketLibevent::NumBytesRead() const {
   return num_bytes_read_;
 }
 
 base::TimeDelta TCPClientSocketLibevent::GetConnectTimeMicros() const {
   return connect_time_micros_;
 }
 
+NextProto TCPClientSocketLibevent::GetNegotiatedProtocol() const {
+  return kProtoUnknown;
+}
+
 }  // namespace net