Add a deprecation message to rtcpMuxPolicy of negotiate.

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

Index: third_party/WebKit/Source/modules/peerconnection/RTCPeerConnection.cpp
diff --git a/third_party/WebKit/Source/modules/peerconnection/RTCPeerConnection.cpp b/third_party/WebKit/Source/modules/peerconnection/RTCPeerConnection.cpp
index 8fd23dbfde05e35696379d469a3dd8f9f52d2975..c216ed0d696e346ea54cd0fc62b41dcaf3a28d0a 100644
--- a/third_party/WebKit/Source/modules/peerconnection/RTCPeerConnection.cpp
+++ b/third_party/WebKit/Source/modules/peerconnection/RTCPeerConnection.cpp
@@ -48,6 +48,7 @@
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/ExecutionContext.h"
+#include "core/frame/Deprecation.h"
 #include "core/frame/HostsUsingFeatures.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/LocalFrameClient.h"
@@ -264,7 +265,7 @@ WebRTCConfiguration parseConfiguration(ExecutionContext* context,
   String rtcpMuxPolicyString = configuration.rtcpMuxPolicy();
   if (rtcpMuxPolicyString == "negotiate") {
     rtcpMuxPolicy = WebRTCRtcpMuxPolicy::kNegotiate;
-    UseCounter::count(context, UseCounter::RtcpMuxPolicyNegotiate);
+    Deprecation::countDeprecation(context, UseCounter::RtcpMuxPolicyNegotiate);
   } else {
     DCHECK_EQ(rtcpMuxPolicyString, "require");
   }