Report metrics about negotiated ciphers.

talk/app/webrtc/webrtcsession.cc

Index: talk/app/webrtc/webrtcsession.cc
diff --git a/talk/app/webrtc/webrtcsession.cc b/talk/app/webrtc/webrtcsession.cc
index 5c8b2df754fe8d69dd5928e2a0477e3f2e8e50ab..c827c790a0fec7bd07e33198f9e2702d6ccb0bf4 100644
--- a/talk/app/webrtc/webrtcsession.cc
+++ b/talk/app/webrtc/webrtcsession.cc
@@ -1393,6 +1393,7 @@ void WebRtcSession::OnTransportCompleted(cricket::Transport* transport) {
   // Only report once when Ice connection is completed.
   if (old_state != PeerConnectionInterface::kIceConnectionCompleted) {
     ReportBestConnectionState(transport);
+    ReportNegotiatedCiphers(transport);

[guoweis_webrtc, 2015/06/08 17:09:11]

Both ReportBestConnectionState and ReportNegotiatedCiphers call GetStats
internally. I could imagine there might be other reporting in the future.
Suggest to have the GetStats outside and pass the state into each function.

[joachim, 2015/06/08 20:58:40]

Done.

   }
 }
 
@@ -1904,4 +1905,24 @@ void WebRtcSession::ReportBestConnectionState(cricket::Transport* transport) {
   }
 }
 
+void WebRtcSession::ReportNegotiatedCiphers(cricket::Transport* transport) {
+  if (!metrics_observer_ || !dtls_enabled_) {
+    return;
+  }
+
+  cricket::TransportStats stats;
+  if (!transport->GetStats(&stats) || stats.channel_stats.empty()) {
+    return;
+  }
+
+  const std::string& srtp_cipher = stats.channel_stats[0].srtp_cipher;
+  const std::string& ssl_cipher = stats.channel_stats[0].ssl_cipher;
+  if (srtp_cipher.empty() || ssl_cipher.empty()) {
+    return;
+  }
+
+  metrics_observer_->CiphersNegotiated(stats.content_name,
+                                       srtp_cipher, ssl_cipher);
+}
+
 }  // namespace webrtc