Refactor Future constructors.

pkg/intl/lib/date_symbol_data_local.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Date/time formatting symbols for all locales.
  *
  * DO NOT EDIT. This file is autogenerated by script.  See
  * 'http://go/generate_datetime_constants.py' using the --for_dart flag.
  *
@@ skipping 13 matching lines @@
 
 /**
  * This should be called for at least one [locale] before any date
  * formatting methods are called. It sets up the lookup for date
  * symbols. Both the [locale] and [ignored] parameter are ignored, as
  * the data for all locales is directly available.
  */
 Future initializeDateFormatting(String locale, String ignored) {
   initializeDateSymbols(dateTimeSymbolMap);
   initializeDatePatterns(dateTimePatternMap);
-  return new Future.immediate(null);
+  return new Future.value();
 }
 
 /**
  * Returns a Map from locale names to the DateSymbols instance for
  * that locale. Internal use only. Call initializeDateFormatting
  * instead.
  */
 Map dateTimeSymbolMap() => {
   /**
    * Date/time formatting symbols for locale en_ISO.
@@ skipping 3516 matching lines @@
            'ikota yesi-4'],
       AMPMS: const [ 'AM', 'PM'],
       DATEFORMATS: const [ 'EEEE dd MMMM y', 'd MMMM y', 'd MMM y',
            'yyyy-MM-dd'],
       TIMEFORMATS: const [ 'h:mm:ss a zzzz', 'h:mm:ss a z', 'h:mm:ss a',
            'h:mm a'],
       FIRSTDAYOFWEEK: 6,
       WEEKENDRANGE: const [5, 6],
       FIRSTWEEKCUTOFFDAY: 5)
 };