Move optional.h to webrtc/api/

webrtc/api/audio_codecs/audio_format.h

 /*
  *  Copyright (c) 2016 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_AUDIO_CODECS_AUDIO_FORMAT_H_
 #define WEBRTC_API_AUDIO_CODECS_AUDIO_FORMAT_H_
 
 #include <map>
 #include <ostream>
 #include <string>
 #include <utility>
 
-#include "webrtc/rtc_base/optional.h"
+#include "webrtc/api/optional.h"
 
 namespace webrtc {
 
 // SDP specification for a single audio codec.
 // NOTE: This class is still under development and may change without notice.
 struct SdpAudioFormat {
   using Parameters = std::map<std::string, std::string>;
 
   SdpAudioFormat(const SdpAudioFormat&);
   SdpAudioFormat(SdpAudioFormat&&);
@@ skipping 103 matching lines @@
 
   SdpAudioFormat format;
   AudioCodecInfo info;
 };
 
 std::ostream& operator<<(std::ostream& os, const AudioCodecSpec& acs);
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_AUDIO_CODECS_AUDIO_FORMAT_H_