Windows: use SystemTimeToTzSpecificLocalTime instead of localtime_s.

src/base/platform/platform-win32.cc

Index: src/base/platform/platform-win32.cc
diff --git a/src/base/platform/platform-win32.cc b/src/base/platform/platform-win32.cc
index 9b554b221e5af779a900c1445e0f2bf7669ec273..1c46cf6811b02eafa27979405046ffb12135dad3 100644
--- a/src/base/platform/platform-win32.cc
+++ b/src/base/platform/platform-win32.cc
@@ -346,41 +346,26 @@ void Win32Time::SetToCurrentTime() {
 }
 
 
+int64_t FileTimeToInt64(FILETIME ft) {
+  ULARGE_INTEGER result;
+  result.LowPart = ft.dwLowDateTime;
+  result.HighPart = ft.dwHighDateTime;
+  return static_cast<int64_t>(result.QuadPart);
+}
+
+
 // Return the local timezone offset in milliseconds east of UTC. This
 // takes into account whether daylight saving is in effect at the time.
 // Only times in the 32-bit Unix range may be passed to this function.
 // Also, adding the time-zone offset to the input must not overflow.
 // The function EquivalentTime() in date.js guarantees this.
 int64_t Win32Time::LocalOffset(TimezoneCache* cache) {
-  cache->InitializeIfNeeded();
-
-  Win32Time rounded_to_second(*this);
-  rounded_to_second.t() = rounded_to_second.t() / 1000 / kTimeScaler *
-      1000 * kTimeScaler;
-  // Convert to local time using POSIX localtime function.
-  // Windows XP Service Pack 3 made SystemTimeToTzSpecificLocalTime()
-  // very slow.  Other browsers use localtime().
-
-  // Convert from JavaScript milliseconds past 1/1/1970 0:00:00 to
-  // POSIX seconds past 1/1/1970 0:00:00.
-  double unchecked_posix_time = rounded_to_second.ToJSTime() / 1000;
-  if (unchecked_posix_time > INT_MAX || unchecked_posix_time < 0) {
-    return 0;
-  }
-  // Because _USE_32BIT_TIME_T is defined, time_t is a 32-bit int.
-  time_t posix_time = static_cast<time_t>(unchecked_posix_time);
-
-  // Convert to local time, as struct with fields for day, hour, year, etc.
-  tm posix_local_time_struct;
-  if (localtime_s(&posix_local_time_struct, &posix_time)) return 0;
-
-  if (posix_local_time_struct.tm_isdst > 0) {
-    return (cache->tzinfo_.Bias + cache->tzinfo_.DaylightBias) * -kMsPerMinute;
-  } else if (posix_local_time_struct.tm_isdst == 0) {
-    return (cache->tzinfo_.Bias + cache->tzinfo_.StandardBias) * -kMsPerMinute;
-  } else {
-    return cache->tzinfo_.Bias * -kMsPerMinute;
-  }
+  FILETIME local;
+  SYSTEMTIME system_utc, system_local;
+  FileTimeToSystemTime(&time_.ft_, &system_utc);
+  SystemTimeToTzSpecificLocalTime(NULL, &system_utc, &system_local);
+  SystemTimeToFileTime(&system_local, &local);
+  return (FileTimeToInt64(local) - FileTimeToInt64(time_.ft_)) / kTimeScaler;
 }