Add FileSystemEntity.absolutePath and .isAbsolute properties.

sdk/lib/io/directory_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 _Directory extends FileSystemEntity implements Directory {
   static const CREATE_REQUEST = 0;
   static const DELETE_REQUEST = 1;
   static const EXISTS_REQUEST = 2;
@@ skipping 56 matching lines @@
   }
 
   bool existsSync() {
     var result = _exists(path);
     if (result is OSError) {
       throw new DirectoryException("Exists failed", path, result);
     }
     return (result == 1);
   }
 
+  Directory get absolute => new Directory(_absolutePath);
+
   Future<FileStat> stat() => FileStat.stat(path);
 
   FileStat statSync() => FileStat.statSync(path);
 
   // Compute the index of the first directory in the list that exists. If
   // none of the directories exist dirsToCreate.length is returned.
   Future<int> _computeExistingIndex(List dirsToCreate) {
     var future;
     var notFound = dirsToCreate.length;
     for (var i = 0; i < dirsToCreate.length; i++) {
@@ skipping 319 matching lines @@
       controller.addError(
           new DirectoryException("Directory listing failed",
                                  errorPath,
                                  err));
     } else {
       controller.addError(
           new DirectoryException("Internal error"));
     }
   }
 }