RAPPOR metric for usage of RTCPeerConnection without connecting.

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 4a24c286721e4ed3802f033fc81cacd90bc37285..7bcd1d2e8343cd77a625cca2e4ddfa0dbcfa6256 100644
--- a/third_party/WebKit/Source/modules/peerconnection/RTCPeerConnection.cpp
+++ b/third_party/WebKit/Source/modules/peerconnection/RTCPeerConnection.cpp
@@ -1412,6 +1412,9 @@ void RTCPeerConnection::closeInternal() {
   changeIceConnectionState(ICEConnectionStateClosed);
   changeIceGatheringState(ICEGatheringStateComplete);
   changeSignalingState(SignalingStateClosed);
+  Document* document = toDocument(getExecutionContext());
+  HostsUsingFeatures::countAnyWorld(
+      *document, HostsUsingFeatures::Feature::RTCPeerConnectionUsed);
 }
 
 void RTCPeerConnection::scheduleDispatchEvent(Event* event) {