Add NSS function to retrieve TLS client cert types requested by server.

net/third_party/nss/ssl/ssl.h

 /*
  * This file contains prototypes for the public SSL functions.
  *
  * ***** BEGIN LICENSE BLOCK *****
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  *
  * The contents of this file are subject to the Mozilla Public License Version
  * 1.1 (the "License"); you may not use this file except in compliance with
  * the License. You may obtain a copy of the License at
  * http://www.mozilla.org/MPL/
@@ skipping 780 matching lines @@
 ** Did the handshake with the peer negotiate the given extension?
 ** Output parameter valid only if function returns SECSuccess
 */
 SSL_IMPORT SECStatus SSL_HandshakeNegotiatedExtension(PRFileDesc * socket,
                                                       SSLExtensionType extId,
                                                       PRBool *yes);
 
 SSL_IMPORT SECStatus SSL_HandshakeResumedSession(PRFileDesc *fd,
                                                  PRBool *last_handshake_resumed);
 
+/* Returns a SECItem containing the certificate_types field of the
+** CertificateRequest message.  Each byte of the data is a TLS
+** ClientCertificateType value, and they are ordered from most preferred to
+** least.  This function should only be called from the
+** SSL_GetClientAuthDataHook callback, and will return NULL if called at any
+** other time.  The returned value is valid only until the callback returns, and
+** should not be freed.
+*/
+SSL_IMPORT const SECItem *
+SSL_GetRequestedClientCertificateTypes(PRFileDesc *fd);
 
 SEC_END_PROTOS
 
 #endif /* __ssl_h_ */