[presubmit] Enable runtime/threadsafe_fn linter checking.

src/base/platform/platform-cygwin.cc

Index: src/base/platform/platform-cygwin.cc
diff --git a/src/base/platform/platform-cygwin.cc b/src/base/platform/platform-cygwin.cc
index e09fc683956ed481f5eaf3feeaf0744155a2cf4d..18f151ac293383e0516ed6078ac1dbfbf79bc9b0 100644
--- a/src/base/platform/platform-cygwin.cc
+++ b/src/base/platform/platform-cygwin.cc
@@ -29,7 +29,7 @@ namespace base {
 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);
+  struct tm* t = localtime(&tv);  // NOLINT(runtime/threadsafe_fn)
   if (NULL == t) return "";
   return tzname[0];  // The location of the timezone string on Cygwin.
 }
@@ -39,7 +39,7 @@ double OS::LocalTimeOffset(TimezoneCache* cache) {
   // On Cygwin, struct tm does not contain a tm_gmtoff field.
   time_t utc = time(NULL);
   DCHECK(utc != -1);
-  struct tm* loc = localtime(&utc);
+  struct tm* loc = localtime(&utc);  // NOLINT(runtime/threadsafe_fn)
   DCHECK(loc != NULL);
   // time - localtime includes any daylight savings offset, so subtract it.
   return static_cast<double>((mktime(loc) - utc) * msPerSecond -