[date] Add ICU backend for timezone info behind a flag

src/date.cc

Index: src/date.cc
diff --git a/src/date.cc b/src/date.cc
index 6471bdb00af5074f20e71805cada1101b5b923b3..41ec17c25a0db2765c9d1333e7c3505ea0c8817f 100644
--- a/src/date.cc
+++ b/src/date.cc
@@ -7,6 +7,10 @@
 #include "src/objects.h"
 #include "src/objects-inl.h"
 
+#ifdef V8_I18N_SUPPORT
+#include "src/i18n.h"
+#endif
+
 namespace v8 {
 namespace internal {
 
@@ -21,6 +25,18 @@ static const int kYearsOffset = 400000;
 static const char kDaysInMonths[] =
     {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
 
+DateCache::DateCache()
+    : stamp_(0),
+      tz_cache_(
+#ifdef V8_I18N_SUPPORT
+          FLAG_icu_timezone_data ? new ICUTimezoneCache()
+                                 : base::OS::CreateTimezoneCache()
+#else
+          base::OS::CreateTimezoneCache()
+#endif
+              ) {
+  ResetDateCache();
+}
 
 void DateCache::ResetDateCache() {
   static const int kMaxStamp = Smi::kMaxValue;