Move optional.h to webrtc/api/

webrtc/modules/audio_coding/codecs/isac/audio_decoder_isac_t.h

 /*
  *  Copyright (c) 2015 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_MODULES_AUDIO_CODING_CODECS_ISAC_AUDIO_DECODER_ISAC_T_H_
 #define WEBRTC_MODULES_AUDIO_CODING_CODECS_ISAC_AUDIO_DECODER_ISAC_T_H_
 
 #include <vector>
 
 #include "webrtc/api/audio_codecs/audio_decoder.h"
+#include "webrtc/api/optional.h"
 #include "webrtc/modules/audio_coding/codecs/isac/locked_bandwidth_info.h"
 #include "webrtc/rtc_base/constructormagic.h"
-#include "webrtc/rtc_base/optional.h"
 #include "webrtc/rtc_base/scoped_ref_ptr.h"
 
 namespace webrtc {
 
 template <typename T>
 class AudioDecoderIsacT final : public AudioDecoder {
  public:
   explicit AudioDecoderIsacT(int sample_rate_hz);
   AudioDecoderIsacT(int sample_rate_hz,
                     const rtc::scoped_refptr<LockedIsacBandwidthInfo>& bwinfo);
@@ skipping 20 matching lines @@
   typename T::instance_type* isac_state_;
   int sample_rate_hz_;
   rtc::scoped_refptr<LockedIsacBandwidthInfo> bwinfo_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(AudioDecoderIsacT);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_CODING_CODECS_ISAC_AUDIO_DECODER_ISAC_T_H_