RTCPeerConnection.ontrack event added.

third_party/WebKit/Source/modules/peerconnection/RTCTrackEvent.idl

Index: third_party/WebKit/Source/modules/peerconnection/RTCTrackEvent.idl
diff --git a/third_party/WebKit/Source/modules/peerconnection/RTCTrackEvent.idl b/third_party/WebKit/Source/modules/peerconnection/RTCTrackEvent.idl
new file mode 100644
index 0000000000000000000000000000000000000000..d9dd31c02bffd34be44d4b12afdce8d4e548583d
--- /dev/null
+++ b/third_party/WebKit/Source/modules/peerconnection/RTCTrackEvent.idl
@@ -0,0 +1,16 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// https://w3c.github.io/webrtc-pc/#rtctrackevent
+[
+    RuntimeEnabled=RTCRtpSender,
+    Constructor(DOMString type, RTCTrackEventInit eventInitDict)
+] interface RTCTrackEvent : Event {
+    readonly attribute RTCRtpReceiver           receiver;
+    readonly attribute MediaStreamTrack         track;
+    [SameObject]
+    readonly attribute FrozenArray<MediaStream> streams;
+    // TODO(hbos): When RTCRtpTransceiver is supported, add:
+    // readonly attribute RTCRtpTransceiver        transceiver;
+};