Add missing #include <cerrno> in string_to_number.cc

webrtc/base/string_to_number.cc

 /*
  *  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.
  */
 
+#include <cerrno>
 #include <cstdlib>
 
 #include "webrtc/base/string_to_number.h"
 
 namespace rtc {
 namespace string_to_number_internal {
 
 rtc::Optional<signed_type> ParseSigned(const char* str, int base) {
   RTC_DCHECK(str);
   if (isdigit(str[0]) || str[0] == '-') {
@@ skipping 19 matching lines @@
     const unsigned_type value = std::strtoull(str, &end, base);
     if (end && *end == '\0' && errno == 0 && (value == 0 || !is_negative)) {
       return rtc::Optional<unsigned_type>(value);
     }
   }
   return rtc::Optional<unsigned_type>();
 }
 
 }  // namespace string_to_number_internal
 }  // namespace rtc