dart:io | Add asynchronous versions of the methods of FileSystemEntity and Link.

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;
 
 // Read the file in blocks of size 64k.
 const int _BLOCK_SIZE = 64 * 1024;
 
 
@@ skipping 187 matching lines @@
 const int _LENGTH_FROM_PATH_REQUEST = 11;
 const int _LAST_MODIFIED_REQUEST = 12;
 const int _FLUSH_REQUEST = 13;
 const int _READ_BYTE_REQUEST = 14;
 const int _WRITE_BYTE_REQUEST = 15;
 const int _READ_REQUEST = 16;
 const int _READ_LIST_REQUEST = 17;
 const int _WRITE_LIST_REQUEST = 18;
 const int _CREATE_LINK_REQUEST = 19;
 const int _DELETE_LINK_REQUEST = 20;
+const int _LINK_TARGET_REQUEST = 21;
 
 // Base class for _File and _RandomAccessFile with shared functions.
 class _FileBase {
   bool _isErrorResponse(response) {
     return response is List && response[0] != _SUCCESS_RESPONSE;
   }
 
   _exceptionFromResponse(response, String message) {
     assert(_isErrorResponse(response));
     switch (response[_ERROR_RESPONSE_ERROR_TYPE]) {
@@ skipping 819 matching lines @@
           new FileIOException("File closed '$_path'"));
     });
     return completer.future;
   }
 
   final String _path;
   int _id;
 
   SendPort _fileService;
 }