RTCRtpSender with track behind RuntimeEnabled flag

third_party/WebKit/public/platform/WebRTCRtpSender.h

Index: third_party/WebKit/public/platform/WebRTCRtpSender.h
diff --git a/third_party/WebKit/public/platform/WebRTCRtpSender.h b/third_party/WebKit/public/platform/WebRTCRtpSender.h
new file mode 100644
index 0000000000000000000000000000000000000000..ebf9523150ffbea33d446827874b481bdd919cc4
--- /dev/null
+++ b/third_party/WebKit/public/platform/WebRTCRtpSender.h
@@ -0,0 +1,32 @@
+// 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.
+
+#ifndef WebRTCRtpSender_h
+#define WebRTCRtpSender_h
+
+#include "WebCommon.h"
+#include "WebString.h"
+
+namespace blink {
+
+class WebMediaStreamTrack;
+
+// Implementations of this interface keep the corresponding WebRTC-layer sender
+// alive through reference counting. Multiple |WebRTCRtpSender|s could reference
+// the same sender; check for equality with |id|.
+// https://w3c.github.io/webrtc-pc/#rtcrtpsender-interface
+class BLINK_PLATFORM_EXPORT WebRTCRtpSender {
+ public:
+  virtual ~WebRTCRtpSender();
+
+  // Two |WebRTCRtpSender|s referencing the same WebRTC-layer sender have the
+  // same |id|. IDs are guaranteed to be unique amongst senders but they are
+  // allowed to be reused after a sender is destroyed.
+  virtual uintptr_t Id() const = 0;
+  virtual const WebMediaStreamTrack* Track() const = 0;
+};
+
+}  // namespace blink
+
+#endif  // WebRTCRtpSender_h