Reapply "Add support for timezone offset and timezone name."

runtime/lib/date.cc

Index: runtime/lib/date.cc
diff --git a/runtime/lib/date.cc b/runtime/lib/date.cc
index 90158c9a345475fcf072595be66597ccd2079842..0c49e5b3fa0557e2e4d7d7e8d8d3891770cd54bb 100644
--- a/runtime/lib/date.cc
+++ b/runtime/lib/date.cc
@@ -139,6 +139,32 @@ DEFINE_NATIVE_ENTRY(DateNatives_brokenDownToSecondsSinceEpoch, 7) {
 }
 
 
+DEFINE_NATIVE_ENTRY(DateNatives_timeZoneName, 1) {
+  GET_NATIVE_ARGUMENT(Integer, dart_seconds, arguments->At(0));
+  int64_t seconds = dart_seconds.AsInt64Value();
+  const char* name;
+  bool succeeded = OS::GetTimeZoneName(seconds, &name);
+  if (!succeeded) {
+    UNIMPLEMENTED();
+  }
+  const String& dart_name = String::Handle(String::New(name));
+  arguments->SetReturn(dart_name);
+}
+
+
+DEFINE_NATIVE_ENTRY(DateNatives_timeZoneOffsetInSeconds, 1) {
+  GET_NATIVE_ARGUMENT(Integer, dart_seconds, arguments->At(0));
+  int64_t seconds = dart_seconds.AsInt64Value();
+  int offset;
+  bool succeeded = OS::GetTimeZoneOffsetInSeconds(seconds, &offset);
+  if (!succeeded) {
+    UNIMPLEMENTED();
+  }
+  const Integer& dart_offset = Integer::Handle(Integer::New(offset));
+  arguments->SetReturn(dart_offset);
+}
+
+
 DEFINE_NATIVE_ENTRY(DateNatives_currentTimeMillis, 0) {
   const Integer& time = Integer::Handle(
       Integer::New(OS::GetCurrentTimeMillis()));