[base] Use thread safe localtime_r() instead of localtime().

src/base/platform/platform-macos.cc

Index: src/base/platform/platform-macos.cc
diff --git a/src/base/platform/platform-macos.cc b/src/base/platform/platform-macos.cc
index 91bc8d6714edc16c5765ba6a64639915c61c7a25..b75bc47e31febcbc1e244f89bfcf24e8b7324102 100644
--- a/src/base/platform/platform-macos.cc
+++ b/src/base/platform/platform-macos.cc
@@ -102,7 +102,8 @@ void OS::SignalCodeMovingGC() {
 const char* OS::LocalTimezone(double time, TimezoneCache* cache) {
   if (std::isnan(time)) return "";
   time_t tv = static_cast<time_t>(std::floor(time/msPerSecond));
-  struct tm* t = localtime(&tv);  // NOLINT(runtime/threadsafe_fn)
+  struct tm tm;
+  struct tm* t = localtime_r(&tv, &tm);
   if (NULL == t) return "";
   return t->tm_zone;
 }
@@ -110,7 +111,8 @@ const char* OS::LocalTimezone(double time, TimezoneCache* cache) {
 
 double OS::LocalTimeOffset(TimezoneCache* cache) {
   time_t tv = time(NULL);
-  struct tm* t = localtime(&tv);  // NOLINT(runtime/threadsafe_fn)
+  struct tm tm;
+  struct tm* t = localtime_r(&tv, &tm);
   // tm_gmtoff includes any daylight savings offset, so subtract it.
   return static_cast<double>(t->tm_gmtoff * msPerSecond -
                              (t->tm_isdst > 0 ? 3600 * msPerSecond : 0));