Move optional.h to webrtc/api/

webrtc/api/ortc/rtptransportinterface.h

 /*
  *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_API_ORTC_RTPTRANSPORTINTERFACE_H_
 #define WEBRTC_API_ORTC_RTPTRANSPORTINTERFACE_H_
 
 #include <string>
 
+#include "webrtc/api/optional.h"
 #include "webrtc/api/ortc/packettransportinterface.h"
 #include "webrtc/api/rtcerror.h"
 #include "webrtc/common_types.h"
-#include "webrtc/rtc_base/optional.h"
 
 namespace webrtc {
 
 class RtpTransportAdapter;
 
 struct RtcpParameters final {
   // The SSRC to be used in the "SSRC of packet sender" field. If not set, one
   // will be chosen by the implementation.
   // TODO(deadbeef): Not implemented.
   rtc::Optional<uint32_t> ssrc;
@@ skipping 84 matching lines @@
   friend class OrtcFactory;
   friend class OrtcRtpSenderAdapter;
   friend class OrtcRtpReceiverAdapter;
   friend class RtpTransportControllerAdapter;
   friend class RtpTransportAdapter;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_ORTC_RTPTRANSPORTINTERFACE_H_