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

net/socket/socks_client_socket.cc

Index: net/socket/socks_client_socket.cc
diff --git a/net/socket/socks_client_socket.cc b/net/socket/socks_client_socket.cc
index f081563464e7de2935ac16fd3a06404db0765643..01983d916b67e018dc080e4a0c6905df1ba32624 100644
--- a/net/socket/socks_client_socket.cc
+++ b/net/socket/socks_client_socket.cc
@@ -181,6 +181,14 @@ base::TimeDelta SOCKSClientSocket::GetConnectTimeMicros() const {
   return base::TimeDelta::FromMicroseconds(-1);
 }
 
+NextProto SOCKSClientSocket::GetNegotiatedProtocol() const {
+  if (transport_.get() && transport_->socket()) {
+    return transport_->socket()->GetNegotiatedProtocol();
+  }
+  NOTREACHED();
+  return kProtoUnknown;
+}
+
 // Read is called by the transport layer above to read. This can only be done
 // if the SOCKS handshake is complete.
 int SOCKSClientSocket::Read(IOBuffer* buf, int buf_len,