Move optional.h to webrtc/api/

webrtc/modules/audio_processing/aec3/echo_remover.h

 /*
  *  Copyright (c) 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_MODULES_AUDIO_PROCESSING_AEC3_ECHO_REMOVER_H_
 #define WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_ECHO_REMOVER_H_
 
 #include <vector>
 
+#include "webrtc/api/optional.h"
 #include "webrtc/modules/audio_processing/aec3/echo_path_variability.h"
 #include "webrtc/modules/audio_processing/aec3/render_buffer.h"
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
-#include "webrtc/rtc_base/optional.h"
 
 namespace webrtc {
 
 // Class for removing the echo from the capture signal.
 class EchoRemover {
  public:
   static EchoRemover* Create(
       const AudioProcessing::Config::EchoCanceller3& config,
       int sample_rate_hz);
   virtual ~EchoRemover() = default;
 
   // Removes the echo from a block of samples from the capture signal. The
   // supplied render signal is assumed to be pre-aligned with the capture
   // signal.
   virtual void ProcessCapture(
       const rtc::Optional<size_t>& echo_path_delay_samples,
       const EchoPathVariability& echo_path_variability,
       bool capture_signal_saturation,
       const RenderBuffer& render_buffer,
       std::vector<std::vector<float>>* capture) = 0;
 
   // Updates the status on whether echo leakage is detected in the output of the
   // echo remover.
   virtual void UpdateEchoLeakageStatus(bool leakage_detected) = 0;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_ECHO_REMOVER_H_