Move optional.h to webrtc/api/

webrtc/modules/audio_processing/aec3/render_delay_controller_metrics.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_RENDER_DELAY_CONTROLLER_METRICS_H_
 #define WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_RENDER_DELAY_CONTROLLER_METRICS_H_
 
+#include "webrtc/api/optional.h"
 #include "webrtc/rtc_base/constructormagic.h"
-#include "webrtc/rtc_base/optional.h"
 
 namespace webrtc {
 
 // Handles the reporting of metrics for the render delay controller.
 class RenderDelayControllerMetrics {
  public:
   RenderDelayControllerMetrics() = default;
 
   // Updates the metric with new data.
   void Update(rtc::Optional<size_t> delay_samples, size_t buffer_delay_blocks);
@@ skipping 12 matching lines @@
   int initial_call_counter_ = 0;
   bool metrics_reported_ = false;
   bool initial_update = true;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(RenderDelayControllerMetrics);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_RENDER_DELAY_CONTROLLER_METRICS_H_