Log how often DTLS negotiation failed because of incompatible ciphersuites.

webrtc/base/opensslstreamadapter.cc

Index: webrtc/base/opensslstreamadapter.cc
diff --git a/webrtc/base/opensslstreamadapter.cc b/webrtc/base/opensslstreamadapter.cc
index b856f3cdb31c8ee222621ce53a16e11271894c75..4b40c389049c326ee5cc4330077ea0cead954e57 100644
--- a/webrtc/base/opensslstreamadapter.cc
+++ b/webrtc/base/opensslstreamadapter.cc
@@ -839,6 +839,12 @@ int OpenSSLStreamAdapter::ContinueSSL() {
     case SSL_ERROR_ZERO_RETURN:
     default:
       LOG(LS_VERBOSE) << " -- error " << code;
+      SSLHandshakeError ssl_handshake_err = SSLHandshakeError::UNKNOWN;
+      int err_code = ERR_peek_last_error();
+      if (err_code != 0 && ERR_GET_REASON(err_code) == SSL_R_NO_SHARED_CIPHER) {
+        ssl_handshake_err = SSLHandshakeError::INCOMPATIBLE_CIPHERSUITE;
+      }
+      SignalSSLHandshakeError(ssl_handshake_err);
       return (ssl_error != 0) ? ssl_error : -1;
   }