[dart:io] Reland: Adds Platform.localeName

sdk/lib/io/platform_impl.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.
 
 part of dart.io;
 
 class _Platform {
   external static int _numberOfProcessors();
   external static String _pathSeparator();
   external static String _operatingSystem();
@@ skipping 14 matching lines @@
    * Values are everything after the first '=' character.
    * A value may contain further '=' characters, and it may be empty.
    *
    * Returns an [OSError] if retrieving the environment fails.
    */
   external static _environment();
   external static List<String> _executableArguments();
   external static String _packageRoot();
   external static String _packageConfig();
   external static String _version();
+  external static String _localeName();
 
   static String executable = _executable();
   static String resolvedExecutable = _resolvedExecutable();
   static String packageRoot = _packageRoot();
   static String packageConfig = _packageConfig();
 
+  static String _cachedLocaleName;
+  static String get localeName {
+    if (_cachedLocaleName == null) {
+      var result = _localeName();
+      if (result is OSError) {
+        throw result;
+      }
+      _cachedLocaleName = result;
+    }
+    return _cachedLocaleName;
+  }
+
   // Cache the OS environment. This can be an OSError instance if
   // retrieving the environment failed.
   static var /*OSError|Map<String,String>*/ _environmentCache;
 
   static int get numberOfProcessors => _numberOfProcessors();
   static String get pathSeparator => _pathSeparator();
   static String get operatingSystem => _operatingSystem();
   static Uri script;
 
   static String get localHostname {
@@ skipping 76 matching lines @@
     _map.forEach(f);
   }
 
   Iterable<String> get keys => _map.keys;
   Iterable<V> get values => _map.values;
   int get length => _map.length;
   bool get isEmpty => _map.isEmpty;
   bool get isNotEmpty => _map.isNotEmpty;
   String toString() => _map.toString();
 }