Add a use counter for RtcpMuxPolicy of "negotiate".

third_party/WebKit/Source/modules/peerconnection/RTCPeerConnection.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 245 matching lines @@
   } else if (bundlePolicyString == "max-bundle") {
     bundlePolicy = WebRTCBundlePolicy::kMaxBundle;
   } else {
     DCHECK_EQ(bundlePolicyString, "balanced");
   }
 
   WebRTCRtcpMuxPolicy rtcpMuxPolicy = WebRTCRtcpMuxPolicy::kRequire;
   String rtcpMuxPolicyString = configuration.rtcpMuxPolicy();
   if (rtcpMuxPolicyString == "negotiate") {
     rtcpMuxPolicy = WebRTCRtcpMuxPolicy::kNegotiate;
+    UseCounter::count(context, UseCounter::RtcpMuxPolicyNegotiate);
   } else {
     DCHECK_EQ(rtcpMuxPolicyString, "require");
   }
   WebRTCConfiguration webConfiguration;
   webConfiguration.iceTransportPolicy = iceTransportPolicy;
   webConfiguration.bundlePolicy = bundlePolicy;
   webConfiguration.rtcpMuxPolicy = rtcpMuxPolicy;
 
   if (configuration.hasIceServers()) {
     Vector<WebRTCIceServer> iceServers;
@@ skipping 1206 matching lines @@
 DEFINE_TRACE(RTCPeerConnection) {
   visitor->trace(m_localStreams);
   visitor->trace(m_remoteStreams);
   visitor->trace(m_dispatchScheduledEventRunner);
   visitor->trace(m_scheduledEvents);
   EventTargetWithInlineData::trace(visitor);
   SuspendableObject::trace(visitor);
 }
 
 }  // namespace blink