Make verifiedLocale work differently depending on what it's verifying for

pkg/intl/lib/date_format.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.
 
 /**
  * DateFormat is for formatting and parsing dates in a locale-sensitive
  * manner.
  * It allows the user to choose from a set of standard date time formats as well
  * as specify a customized pattern under certain locales. Date elements that
  * vary across locales include month name, week name, field order, etc.
@@ skipping 166 matching lines @@
    *
    * If [locale] does not exist in our set of supported locales then an
    * [ArgumentError] is thrown.
    */
   DateFormat([String newPattern, String locale]) {
     // TODO(alanknight): It should be possible to specify multiple skeletons eg
     // date, time, timezone all separately. Adding many or named parameters to
     // the constructor seems awkward, especially with the possibility of
     // confusion with the locale. A "fluent" interface with cascading on an
     // instance might work better? A list of patterns is also possible.
-    _locale = Intl.verifiedLocale(locale);
+    _locale = Intl.verifiedLocale(locale, localeExists);
     addPattern(newPattern);
   }
 
   /**
    * Return a string representing [date] formatted according to our locale
    * and internal format.
    */
   String format(Date date) {
     // TODO(efortuna): read optional TimeZone argument (or similar)?
     var result = new StringBuffer();
@@ skipping 303 matching lines @@
   }
 
   /**
    * Set the locale. If the locale can't be found, we also look up
    * based on alternative versions, e.g. if we have no 'en_CA' we will
    * look for 'en' as a fallback. It will also translate en-ca into en_CA.
    * Null is also considered a valid value for [newLocale], indicating
    * to use the default.
    */
   _setLocale(String newLocale) {
-    _locale = Intl.verifiedLocale(newLocale);
+    _locale = Intl.verifiedLocale(newLocale, localeExists);
   }
 
   /**
    * Return true if the locale exists, or if it is null. The null case
    * is interpreted to mean that we use the default locale.
    */
   static bool localeExists(localeName) {
     if (localeName == null) return false;
     return dateTimeSymbols.containsKey(localeName);
   }
@@ skipping 37 matching lines @@
   List _reverse(List list) {
     // TODO(alanknight): Use standardized list reverse when implemented.
     // See Issue 2804.
     var result = new List();
     for (var i = list.length-1; i >= 0; i--) {
       result.addLast(list[i]);
     }
     return result;
   }
 }