[dart:io] Adds functions to set file access and modification time

sdk/lib/io/file_system_entity.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;
 
 /**
  * The type of an entity on the file system, such as a file, directory, or link.
  *
  * These constants are used by the [FileSystemEntity] class
@@ skipping 341 matching lines @@
    * Calls the operating system's stat() function on the [path] of this
    * [FileSystemEntity].  Identical to [:FileStat.stat(this.path):].
    *
    * Returns a [:Future<FileStat>:] object containing the data returned by
    * stat().
    *
    * If the call fails, completes the future with a [FileStat] object
    * with .type set to
    * FileSystemEntityType.NOT_FOUND and the other fields invalid.
    */
-  Future<FileStat> stat();
+  Future<FileStat> stat() => FileStat.stat(path);
 
   /**
    * Synchronously calls the operating system's stat() function on the
    * [path] of this [FileSystemEntity].
    * Identical to [:FileStat.statSync(this.path):].
    *
    * Returns a [FileStat] object containing the data returned by stat().
    *
    * If the call fails, returns a [FileStat] object with .type set to
    * FileSystemEntityType.NOT_FOUND and the other fields invalid.
    */
-  FileStat statSync();
+  FileStat statSync() => FileStat.statSync(path);
 
   /**
    * Deletes this [FileSystemEntity].
    *
    * If the [FileSystemEntity] is a directory, and if [recursive] is false,
    * the directory must be empty. Otherwise, if [recursive] is true, the
    * directory and all sub-directories and files in the directories are
    * deleted. Links are not followed when deleting recursively. Only the link
    * is deleted, not its target.
    *
@@ skipping 446 matching lines @@
     return buffer.toString();
   }
 }
 
 
 class _FileSystemWatcher {
   external static Stream<FileSystemEvent> _watch(
       String path, int events, bool recursive);
   external static bool get isSupported;
 }