dart:io | Add Link.targetSync on all platforms.

sdk/lib/io/file_impl.dart

 // Copyright (c) 2013, 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 _FileStream extends Stream<List<int>> {
   // Stream controller.
   StreamController<List<int>> _controller;
@@ skipping 283 matching lines @@
         throw _exceptionFromResponse(response, "Cannot create file '$_path'");
       }
       return this;
     });
   }
 
   external static _create(String path);
 
   external static _createLink(String path, String target);
 
+  external static _linkTarget(String path);
+
   void createSync() {
     var result = _create(_path);
     throwIfError(result, "Cannot create file '$_path'");
   }
 
   Future<File> delete() {
     _ensureFileService();
     List request = new List(2);
     request[0] = _DELETE_REQUEST;
     request[1] = _path;
@@ skipping 729 matching lines @@
           new FileIOException("File closed '$_path'"));
     });
     return completer.future;
   }
 
   final String _path;
   int _id;
 
   SendPort _fileService;
 }