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

pkg/intl/lib/number_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.
 
 #library("number_format");
 
 #import('dart:math');
 
 #import("intl.dart");
 #import("number_symbols.dart");
@@ skipping 34 matching lines @@
    * of formatting then there will only ever be one number being formatted
    * at a time. In languages with threads we'd need to pass this on the stack.
    */
   StringBuffer _buffer;
 
   /**
    * Create a number format that prints in [newPattern] as it applies in
    * [locale].
    */
   NumberFormat([String newPattern, String locale]):
-    _locale = Intl.verifiedLocale(locale) {
+    _locale = Intl.verifiedLocale(locale, localeExists) {
     // TODO(alanknight): There will need to be some kind of async setup
     // operations so as not to bring along every locale in every program.
     _symbols = numberFormatSymbols[_locale];
     _setPattern(newPattern);
   }
 
   /**
    * Return the locale code in which we operate, e.g. 'en_US' or 'pt'.
    */
   String get locale => _locale;
 
   /**
+   * 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 numberFormatSymbols.containsKey(localeName);
+  }
+
+  /**
    * Return the symbols which are used in our locale. Cache them to avoid
    * repeated lookup.
    */
   NumberSymbols get symbols {
     return _symbols;
   }
 
   // TODO(alanknight): Actually use the pattern and locale.
   _setPattern(String x) {}
 
@@ skipping 185 matching lines @@
   }
 
   /**
    * Returns the suffix for [x] based on wether it's positive or negative.
    * In en_US there are no suffixes for positive or negative.
    */
   String _signSuffix(num x) {
     return x.isNegative() ? _negativeSuffix : _positiveSuffix;
   }
 }