Add support for directory renaming to dart:io.

runtime/bin/directory.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.
 
 /**
  * [Directory] objects are used for working with directories.
  */
 interface Directory default _Directory {
   /**
    * Creates a directory object. The path is either a full path or
@@ skipping 75 matching lines @@
   Future<Directory> deleteRecursively();
 
   /**
    * Synchronously deletes this directory and all sub-directories and
    * files in the directories. Throws an exception if the directory
    * cannot be deleted.
    */
   void deleteRecursivelySync();
 
   /**
+   * Rename this directory. Returns a [:Future<Directory>:] that completes
+   * with a [Directory] instance for the renamed directory.
+   *
+   * If newPath identifies an existing directory, that directory is
+   * replaced. If newPath identifies an existing file the operation
+   * fails and the future completes with an exception.
+   */
+  Future<Directory> rename(String newPath);
+
+  /**
+   * Synchronously rename this directory. Returns a [Directory]
+   * instance for the renamed directory.
+   *
+   * If newPath identifies an existing directory, that directory is
+   * replaced. If newPath identifies an existing file the operation
+   * fails and an exception is thrown.
+   */
+  Directory renameSync(String newPath);
+
+  /**
    * List the sub-directories and files of this
    * [Directory]. Optionally recurse into sub-directories. Returns a
    * [DirectoryLister] object representing the active listing
    * operation. Handlers for files and directories should be
    * registered on this DirectoryLister object.
    */
   DirectoryLister list([bool recursive]);
 
   /**
    * Gets the path of this directory.
@@ skipping 59 matching lines @@
       if (path != null) {
         sb.add(", path = $path");
       }
     }
     return sb.toString();
   }
   final String message;
   final String path;
   final OSError osError;
 }