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

net/socket/stream_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_STREAM_SOCKET_H_
 #define NET_SOCKET_STREAM_SOCKET_H_
 #pragma once
 
 #include "base/time.h"
 #include "net/base/net_log.h"
@@ skipping 69 matching lines @@
   // Returns true if the underlying transport socket is using TCP FastOpen.
   // TCP FastOpen is an experiment with sending data in the TCP SYN packet.
   virtual bool UsingTCPFastOpen() const = 0;
 
   // Returns the number of bytes successfully read from this socket.
   virtual int64 NumBytesRead() const = 0;
 
   // Returns the connection setup time of this socket.
   virtual base::TimeDelta GetConnectTimeMicros() const = 0;
 
+  // Returns the protocol negotiated via for this socket, or

[Sergey Ulanov, 2012/04/02 18:20:22]

via NPN?

[Ryan Hamilton, 2012/04/02 20:57:33]

Done.

+  // kProtoUnknown will be returned if NPN is not applicable.

[Sergey Ulanov, 2012/04/02 18:20:22]

I think ideally this shouldn't be part of StreamSocket interface. Can we make a
separate interface called NegotiatingStreamSocket  or NpnStreamSocket that would
inherit from StreamSocket and add this method? That way you wouldn't have to fix
every single implementation of StreamSocket interface. 

[Ryan Hamilton, 2012/04/02 20:57:33]

Yeah, I totally hear you.  The problem comes up because SPDY sessions can be
layered on top of pretty much any kind of socket.  SSL sockets and HTTP proxy
sockets both have the ability to negotiate the SPDY protocol.  However, SPDY
(via command line flags) can also live on top of, for example, a TCP socket.

This seems to imply that pretty much any StreamSocket subclass that SPDY session
can be layered on would need to extend this new class.  But that would be
roughly all of them :| 

It's definitely a thorny issue and we talked about it quite a bit internally.  I
also just chatted with wtc again after reading your comment.  We wish there were
a cleaner solution, but feel that this CL is about as good as we're going to
get.

+  virtual NextProto GetNegotiatedProtocol() const = 0;
+
  protected:
   // The following class is only used to gather statistics about the history of
   // a socket.  It is only instantiated and used in basic sockets, such as
   // TCPClientSocket* instances.  Other classes that are derived from
   // StreamSocket should forward any potential settings to their underlying
   // transport sockets.
   class UseHistory {
    public:
     UseHistory();
     ~UseHistory();
@@ skipping 26 matching lines @@
     // identify the motivation.
     bool omnibox_speculation_;
     bool subresource_speculation_;
     DISALLOW_COPY_AND_ASSIGN(UseHistory);
   };
 };
 
 }  // namespace net
 
 #endif  // NET_SOCKET_STREAM_SOCKET_H_