Add fromUri constructor to File, Directory and Link

sdk/lib/io/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.
 
 part of dart.io;
 
 /**
  * A reference to a directory (or _folder_) on the file system.
  */
 abstract class Directory implements FileSystemEntity {
   /**
    * Creates a directory object. The path is either an absolute path,
    * or it is a relative path which is interpreted relative to the directory
    * in which the Dart VM was started.
    */
   factory Directory(String path) => new _Directory(path);
 
   /**
+   * Create a Directory object from a URI.
+   *
+   * If [uri] cannot reference a directory this throws [UnsupportedError].
+   */
+  factory Directory.fromUri(Uri uri) => new Directory(uri.toFilePath());
+
+  /**
    * Creates a directory object pointing to the current working
    * directory.
    */
   static Directory get current => _Directory.current;
 
   /**
    * Sets the current working directory of the Dart process including
    * all running isolates. The new value set can be either a [Directory]
    * or a [String].
    *
@@ skipping 151 matching lines @@
   /**
    * Returns a human readable string for this Directory instance.
    */
   String toString();
 
   /**
    * Gets the path of this directory.
    */
   final String path;
 }