Move optional.h to webrtc/api/

webrtc/rtc_base/moving_max_counter.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_RTC_BASE_MOVING_MAX_COUNTER_H_
 #define WEBRTC_RTC_BASE_MOVING_MAX_COUNTER_H_
 
 #include <stdint.h>
 
 #include <deque>
 #include <limits>
 #include <utility>
 
+#include "webrtc/api/optional.h"
 #include "webrtc/rtc_base/checks.h"
 #include "webrtc/rtc_base/constructormagic.h"
-#include "webrtc/rtc_base/optional.h"
 
 namespace rtc {
 
 // Implements moving max: can add samples to it and calculate maximum over some
 // fixed moving window.
 //
 // Window size is configured at constructor.
 // Samples can be added with |Add()| and max over current window is returned by
 // |MovingMax|. |current_time_ms| in successive calls to Add and MovingMax
 // should never decrease as if it's a wallclock time.
@@ skipping 74 matching lines @@
   auto it = samples_.begin();
   while (it != samples_.end() && it->first < window_begin_ms) {
     ++it;
   }
   samples_.erase(samples_.begin(), it);
 }
 
 }  // namespace rtc
 
 #endif  // WEBRTC_RTC_BASE_MOVING_MAX_COUNTER_H_