[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 d0ff192b6ad16b05f6bf9e5b652aef17f173f1da..d7eb2d3dccdc8b526794b9979320c11268cb1790 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 +25,15 @@ 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 ICUOSTimezoneCache() :

[ulan, 2017/03/03 13:20:27]

nit: let's keep the conditionals properly nested. If would be easier to read and
check even though it is more code.

#ifdef V8_I18N_SUPPORT
FLAG_icu_timezone_data ? new ICUOSTimezoneCache() : 
                         base::OS::CreateTimezoneCache() 
#else
base::OS::CreateTimezoneCache()
#endif

[Dan Ehrenberg, 2017/03/03 15:06:54]

Done.

+#endif
+                                 base::OS::CreateTimezoneCache()) {
+  ResetDateCache();
+}
 
 void DateCache::ResetDateCache() {
   static const int kMaxStamp = Smi::kMaxValue;