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

lib/compiler/implementation/lib/mockimpl.dart

Index: lib/compiler/implementation/lib/mockimpl.dart
diff --git a/lib/compiler/implementation/lib/mockimpl.dart b/lib/compiler/implementation/lib/mockimpl.dart
index 5994d6d4547d624c33d87b99428c011607932708..2a6171f7adc2f2763a0c80bd84671d385692f1cf 100644
--- a/lib/compiler/implementation/lib/mockimpl.dart
+++ b/lib/compiler/implementation/lib/mockimpl.dart
@@ -297,16 +297,6 @@ class DateImplementation implements Date {
     return new Date.fromEpoch(value, targetTimeZone);
   }
 
-  String get timeZoneName() {
-    if (isUtc()) return "UTC";
-    return Primitives.getTimeZoneName(this);
-  }
-
-  Duration get timeZoneOffset() {
-    if (isUtc()) return new Duration(0);
-    return new Duration(minutes: Primitives.getTimeZoneOffsetInMinutes(this));
-  }
-
   int get year() => Primitives.getYear(this);
 
   int get month() => Primitives.getMonth(this);