Move optional.h to webrtc/api/

webrtc/rtc_base/rate_statistics.h

 /*
  *  Copyright (c) 2013 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_RATE_STATISTICS_H_
 #define WEBRTC_RTC_BASE_RATE_STATISTICS_H_
 
 #include <memory>
 
-#include "webrtc/rtc_base/optional.h"
+#include "webrtc/api/optional.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
 
 class RateStatistics {
  public:
   static constexpr float kBpsScale = 8000.0f;
 
   // max_window_size_ms = Maximum window size in ms for the rate estimation.
   //                      Initial window size is set to this, but may be changed
@@ skipping 48 matching lines @@
   // To convert counts/ms to desired units
   const float scale_;
 
   // The window sizes, in ms, over which the rate is calculated.
   const int64_t max_window_size_ms_;
   int64_t current_window_size_ms_;
 };
 }  // namespace webrtc
 
 #endif  // WEBRTC_RTC_BASE_RATE_STATISTICS_H_