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

src/date.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/date.h"
 
 #include "src/objects.h"
 #include "src/objects-inl.h"
 
+#ifdef V8_I18N_SUPPORT
+#include "src/i18n.h"
+#endif
+
 namespace v8 {
 namespace internal {
 
 
 static const int kDaysIn4Years = 4 * 365 + 1;
 static const int kDaysIn100Years = 25 * kDaysIn4Years - 1;
 static const int kDaysIn400Years = 4 * kDaysIn100Years + 1;
 static const int kDays1970to2000 = 30 * 365 + 7;
 static const int kDaysOffset = 1000 * kDaysIn400Years + 5 * kDaysIn400Years -
                                kDays1970to2000;
 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;
   if (stamp_->value() >= kMaxStamp) {
     stamp_ = Smi::kZero;
   } else {
     stamp_ = Smi::FromInt(stamp_->value() + 1);
   }
   DCHECK(stamp_ != Smi::FromInt(kInvalidStamp));
   for (int i = 0; i < kDSTSize; ++i) {
@@ skipping 332 matching lines @@
     if (result == NULL || result->last_used > dst_[i].last_used) {
       result = &dst_[i];
     }
   }
   ClearSegment(result);
   return result;
 }
 
 }  // namespace internal
 }  // namespace v8