Change File.directory to not do any IO

sdk/lib/io/file.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;
 
 /**
  * FileMode describes the modes in which a file can be opened.
  */
 class FileMode {
@@ skipping 76 matching lines @@
   /**
    * Synchronously delete the file. Only a file or a link to a file
    * can be deleted with this method, not a directory or a broken link.
    *
    * Throws a [FileIOException] if the operation fails.
    */
   void deleteSync();
 
   /**
    * Get a [Directory] object for the directory containing this
-   * file. Returns a [:Future<Directory>:] that completes with the
-   * directory.
+   * file.
    */
-  Future<Directory> directory();
-
-  /**
-   * Synchronously get a [Directory] object for the directory containing
-   * this file.
-   *
-   * Throws a [FileIOException] if the operation fails.
-   */
-  Directory directorySync();
+  Directory get directory;
 
   /**
    * Get the length of the file. Returns a [:Future<int>:] that
    * completes with the length in bytes.
    */
   Future<int> length();
 
   /**
    * Synchronously get the length of the file.
    *
@@ skipping 419 matching lines @@
         sb.write(" ($osError)");
       }
     } else if (osError != null) {
       sb.write(": osError");
     }
     return sb.toString();
   }
   final String message;
   final OSError osError;
 }