Move optional.h to webrtc/api/

webrtc/modules/audio_processing/gain_control_impl.cc

 /*
  *  Copyright (c) 2012 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.
  */
 
 #include "webrtc/modules/audio_processing/gain_control_impl.h"
 
+#include "webrtc/api/optional.h"
 #include "webrtc/modules/audio_processing/agc/legacy/gain_control.h"
 #include "webrtc/modules/audio_processing/audio_buffer.h"
 #include "webrtc/modules/audio_processing/logging/apm_data_dumper.h"
 #include "webrtc/rtc_base/constructormagic.h"
-#include "webrtc/rtc_base/optional.h"
 
 namespace webrtc {
 
 typedef void Handle;
 
 namespace {
 int16_t MapSetting(GainControl::Mode mode) {
   switch (mode) {
     case GainControl::kAdaptiveAnalog:
       return kAgcModeAdaptiveAnalog;
@@ skipping 402 matching lines @@
   for (auto& gain_controller : gain_controllers_) {
     const int handle_error =
         WebRtcAgc_set_config(gain_controller->state(), config);
     if (handle_error != AudioProcessing::kNoError) {
       error = handle_error;
     }
   }
   return error;
 }
 }  // namespace webrtc