Add use counter for offerToReceiveAudio/offerToReceiveVideo

This is to inform the spec discussion:
https://github.com/w3c/webrtc-pc/issues/709

R=guidou@chromium.org

Review-Url: https://codereview.chromium.org/2329433002
Cr-Commit-Position: refs/heads/master@{#417602}

third_party/WebKit/Source/core/frame/UseCounter.h

@@ -1286,6 +1286,8 @@ public:
         MetaRefreshWhenCSPBlocksInlineScript = 1550,
         MiddleClickAutoscrollStart = 1551,
         ClipCssOfFixedPositionElement = 1552,
+        RTCPeerConnectionCreateOfferOptionsOfferToReceive = 1553,
+
         // Add new features immediately above this line. Don't change assigned
         // numbers of any item, and don't reuse removed slots.
         // Also, run update_use_counter_feature_enum.py in chromium/src/tools/metrics/histograms/

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

@@ -500,6 +500,10 @@ ScriptPromise RTCPeerConnection::createOffer(ScriptState* scriptState, const RTC
     ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();
     RTCSessionDescriptionRequest* request = RTCSessionDescriptionRequestPromiseImpl::create(this, resolver);
+    if (options.hasOfferToReceiveAudio() || options.hasOfferToReceiveVideo()) {
+        ExecutionContext* context = scriptState->getExecutionContext();
+        UseCounter::count(context, UseCounter::RTCPeerConnectionCreateOfferOptionsOfferToReceive);
+    }
     m_peerHandler->createOffer(request, convertToWebRTCOfferOptions(options));
     return promise;
 }

tools/metrics/histograms/histograms.xml

@@ -80751,6 +80751,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1550" label="MetaRefreshWhenCSPBlocksInlineScript"/>
   <int value="1551" label="MiddleClickAutoscrollStart"/>
   <int value="1552" label="ClipCssOfFixedPositionElement"/>
+  <int value="1553" label="RTCPeerConnectionCreateOfferOptionsOfferToReceive"/>
 </enum>
 
 <enum name="FetchRequestMode" type="int">