Move optional.h to webrtc/api/

webrtc/modules/audio_coding/codecs/audio_format_conversion.cc

 /*
  *  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.
  */
 
 #include "webrtc/modules/audio_coding/codecs/audio_format_conversion.h"
 
 #include <string.h>
 
 #include "webrtc/api/array_view.h"
+#include "webrtc/api/optional.h"
 #include "webrtc/rtc_base/checks.h"
-#include "webrtc/rtc_base/optional.h"
 #include "webrtc/rtc_base/safe_conversions.h"
 #include "webrtc/rtc_base/sanitizer.h"
 
 namespace webrtc {
 
 namespace {
 
 CodecInst MakeCodecInst(int payload_type,
                         const char* name,
                         int sample_rate,
@@ skipping 51 matching lines @@
       return 1;  // Default to mono.
     }();
     return MakeCodecInst(payload_type, "opus", 48000, num_channels);
   } else {
     return MakeCodecInst(payload_type, audio_format.name.c_str(),
                          audio_format.clockrate_hz, audio_format.num_channels);
   }
 }
 
 }  // namespace webrtc