Add selectedProtocol() to abstract _SecureFilter class

dart/sdk/lib/io/secure_socket.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.io;
 
 /**
  * A high-level class for communicating securely over a TCP socket, using
  * TLS and SSL. The [SecureSocket] exposes both a [Stream] and an
  * [IOSink] interface, making it ideal for using together with
@@ skipping 1346 matching lines @@
                Uint8List addr,
                int port,
                bool is_server,
                String certificateName,
                bool requestClientCertificate,
                bool requireClientCertificate,
                bool sendClientCertificate,
                Uint8List protocols);
   void destroy();
   void handshake();
+  String selectedProtocol();
   void rehandshake();
   void renegotiate(bool useSessionCache,
                    bool requestClientCertificate,
                    bool requireClientCertificate);
   void init();
   X509Certificate get peerCertificate;
   int processBuffer(int bufferIndex);
   void registerBadCertificateCallback(Function callback);
   void registerHandshakeCompleteCallback(Function handshakeCompleteHandler);
   int _pointer();
@@ skipping 45 matching lines @@
 /**
  * An exception that happens in the handshake phase of establishing
  * a secure network connection, when looking up or verifying a
  * certificate.
  */
 class CertificateException extends TlsException {
   const CertificateException([String message = "",
                             OSError osError = null])
      : super._("CertificateException", message, osError);
 }