Implement File.directory() and File.directorySync() to get

runtime/bin/file.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.
 
 
 /**
  * FileMode describes the modes in which a file can be opened.
  */
 class FileMode {
   static final READ = const FileMode(0);
@@ skipping 50 matching lines @@
    * file cannot be deleted.
    */
   void delete();
 
   /**
    * Synchronously delete the file.
    */
   void deleteSync();
 
   /**
+   * Get a Directory object for the directory containing this file. If
+   * the file does not exist the [errorHandler] is called. When the
+   * operation completes the [directoryHandler] is called with the
+   * result.
+   */
+  void directory();
+
+  /**
+   * Synchronously get a Directory object for the directory containing
+   * this file.
+   */
+  Directory directorySync();
+
+  /**
    * Open the file for random access operations. When the file is
    * opened the [openHandler] is called with the resulting
    * RandomAccessFile. RandomAccessFiles must be closed using the
    * [close] method. If the file cannot be opened the [errorHandler]
    * is called.
    *
    * Files can be opened in three modes:
    *
    * FileMode.READ: open the file for reading. If the file does not
    * exist the [errorHandler] is called.
@@ skipping 97 matching lines @@
    */
   void set createHandler(void handler());
 
   /**
    * Sets the handler that gets called when a [delete] operation
    * completes.
    */
   void set deleteHandler(void handler());
 
   /**
+   * Sets the handler that gets called when a [directory] operation
+   * completes.
+   */
+  void set directoryHandler(void handler(Directory directory));
+
+  /**
    * Sets the handler that gets called when an [open] operation
    * completes.
    */
   void set openHandler(void handler(RandomAccessFile openedFile));
 
   /**
    * Sets the handler that gets called when an [openInputStream]
    * operation completes.
    */
   void set inputStreamHandler(void handler(InputStream stream));
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    */
   void set errorHandler(void handler(String error));
 }
 
 
 class FileIOException implements Exception {
   const FileIOException([String this.message = ""]);
   String toString() => "FileIOException: $message";
   final String message;
 }