Move optional.h to webrtc/api/

webrtc/rtc_base/string_to_number.h

 /*
  *  Copyright 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_STRING_TO_NUMBER_H_
 #define WEBRTC_RTC_BASE_STRING_TO_NUMBER_H_
 
 #include <string>
 #include <limits>
 
-#include "webrtc/rtc_base/optional.h"
+#include "webrtc/api/optional.h"
 
 namespace rtc {
 
 // This file declares a family of functions to parse integers from strings.
 // The standard C library functions either fail to indicate errors (atoi, etc.)
 // or are a hassle to work with (strtol, sscanf, etc.). The standard C++ library
 // functions (std::stoi, etc.) indicate errors by throwing exceptions, which
 // are disabled in WebRTC.
 //
 // Integers are parsed using one of the following functions:
@@ skipping 64 matching lines @@
 // version.
 template <typename T>
 auto StringToNumber(const std::string& str, int base = 10)
     -> decltype(StringToNumber<T>(str.c_str(), base)) {
   return StringToNumber<T>(str.c_str(), base);
 }
 
 }  // namespace rtc
 
 #endif  // WEBRTC_RTC_BASE_STRING_TO_NUMBER_H_