Fix a race in initialization of timezone cache in platform-win32.

src/platform-cygwin.cc

Index: src/platform-cygwin.cc
diff --git a/src/platform-cygwin.cc b/src/platform-cygwin.cc
index ac804398f194878e681f5cfd129250e90f02f8a8..4ae9bec9ec4db37872a31c166ae2a6afc78c6d27 100644
--- a/src/platform-cygwin.cc
+++ b/src/platform-cygwin.cc
@@ -51,7 +51,7 @@ namespace v8 {
 namespace internal {
 
 
-const char* OS::LocalTimezone(double time) {
+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);
@@ -60,7 +60,7 @@ const char* OS::LocalTimezone(double time) {
 }
 
 
-double OS::LocalTimeOffset() {
+double OS::LocalTimeOffset(TimezoneCache* cache) {
   // On Cygwin, struct tm does not contain a tm_gmtoff field.
   time_t utc = time(NULL);
   ASSERT(utc != -1);