Add [Measure] to RTCRtpTransceiver APIs.

Measures usage of the following APIs:
- RTCPeerConnection.getTransceivers()
- RTCPeerConneciton.addTransceiver()
- RTCRtpTransceiver.direction (getter/setter)

// The run was green except for unrelated failures with
// mac_chromium_rel_ng that have happened on multiple CLs
NOTRY=True

Bug: 866433
Change-Id: I430680fa3109681c38e82a7b8d2203e7ec18544e
Reviewed-on: https://chromium-review.googlesource.com/1146659
Commit-Queue: Henrik Boström <hbos@chromium.org>
Reviewed-by: Harald Alvestrand <hta@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577179}

third_party/blink/public/platform/web_feature.mojom

@@ -1970,6 +1970,10 @@ enum WebFeature {
   kPopupOpenWhileFileChooserOpened = 2509,
   kCookieStoreAPI = 2510,
   kFeaturePolicyJSAPI = 2511,
+  kV8RTCPeerConnection_GetTransceivers_Method = 2512,
+  kV8RTCPeerConnection_AddTransceiver_Method = 2513,
+  kV8RTCRtpTransceiver_Direction_AttributeGetter = 2514,
+  kV8RTCRtpTransceiver_Direction_AttributeSetter = 2515,
 
   // Add new features immediately above this line. Don't change assigned
   // numbers of any item, and don't reuse removed slots.

third_party/blink/renderer/modules/peerconnection/rtc_peer_connection.idl

@@ -133,14 +133,15 @@ enum RTCIceConnectionState {
 
     // RTP Media API
     // https://w3c.github.io/webrtc-pc/#dom-rtcpeerconnection-gettransceivers
-    sequence<RTCRtpTranceiver> getTransceivers();
+    [Measure] sequence<RTCRtpTranceiver> getTransceivers();
     // https://w3c.github.io/webrtc-pc/#dom-rtcpeerconnection-getsenders
     [Measure] sequence<RTCRtpSender> getSenders();
     // https://w3c.github.io/webrtc-pc/#dom-rtcpeerconnection-getreceivers
     [Measure] sequence<RTCRtpReceiver> getReceivers();
     // https://w3c.github.io/webrtc-pc/#dom-rtcpeerconnection-addtransceiver
-    [RaisesException] RTCRtpTransceiver addTransceiver((MediaStreamTrack or DOMString) track_or_kind,
-                                                       optional RTCRtpTransceiverInit init);
+    [Measure, RaisesException] RTCRtpTransceiver addTransceiver(
+        (MediaStreamTrack or DOMString) track_or_kind,
+        optional RTCRtpTransceiverInit init);
     // https://w3c.github.io/webrtc-pc/#dom-rtcpeerconnection-addtrack
     [Measure, RaisesException] RTCRtpSender addTrack(MediaStreamTrack track, MediaStream... streams);
     // https://w3c.github.io/webrtc-pc/#dom-rtcpeerconnection-removetrack

third_party/blink/renderer/modules/peerconnection/rtc_rtp_transceiver.idl

@@ -17,6 +17,6 @@ interface RTCRtpTransceiver {
     [SameObject] readonly attribute RTCRtpSender sender;
     [SameObject] readonly attribute RTCRtpReceiver receiver;
     readonly attribute boolean stopped;
-    [RaisesException=Setter] attribute RTCRtpTransceiverDirection direction;
+    [Measure, RaisesException=Setter] attribute RTCRtpTransceiverDirection direction;
     readonly attribute RTCRtpTransceiverDirection? currentDirection;
 };

tools/metrics/histograms/enums.xml

@@ -19422,6 +19422,10 @@ Called by update_net_error_codes.py.-->
   <int value="2509" label="PopupOpenWhileFileChooserOpened"/>
   <int value="2510" label="CookieStoreAPI"/>
   <int value="2511" label="FeaturePolicyJSAPI"/>
+  <int value="2512" label="V8RTCPeerConnection_GetTransceivers_Method"/>
+  <int value="2513" label="V8RTCPeerConnection_AddTransceiver_Method"/>
+  <int value="2514" label="V8RTCRtpTransceiver_Direction_AttributeGetter"/>
+  <int value="2515" label="V8RTCRtpTransceiver_Direction_AttributeSetter"/>
 </enum>
 
 <enum name="FeedbackSource">