Log how often DTLS negotiation failed because of incompatible ciphersuites.

webrtc/p2p/base/transportchannelimpl.h

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 82 matching lines @@
 
   virtual bool SetSslRole(rtc::SSLRole role) = 0;
 
   // Invoked when there is conflict in the ICE role between local and remote
   // agents.
   sigslot::signal1<TransportChannelImpl*> SignalRoleConflict;
 
   // Emitted whenever the transport channel state changed.
   sigslot::signal1<TransportChannelImpl*> SignalStateChanged;
 
+  // Emitted whenever the Dtls handshake failed on some transport channel.
+  sigslot::signal1<rtc::SSLHandshakeError> SignalDtlsHandshakeError;
+
  private:
   RTC_DISALLOW_COPY_AND_ASSIGN(TransportChannelImpl);
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_TRANSPORTCHANNELIMPL_H_