Change IllegalArgumentException to ArgumentError.

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 164 matching lines @@
    *
    * For example, in an en_US locale, specifying the skeleton
    *     `new DateFormat('yMEd');`
    * or the explicit
    *     `new DateFormat('EEE, M/d/y');`
    * would produce the same result, a date of the form
    *     `Wed, 6/27/2012`
    * However, the skeleton version would also adapt to other locales.
    *
    * If [locale] does not exist in our set of supported locales then an
-   * [IllegalArgumentException] is thrown.
+   * [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.
     // TODO(alanknight): There will need to be at least setup type async
     // operations to avoid the need to bring along every locale in every program
     _locale = Intl.verifiedLocale(locale);
@@ skipping 351 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;
   }
 }