Add .fromPath constructors to File and Directory.

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._internal(0);
@@ skipping 11 matching lines @@
  * streams using [openInputStream] and [openOutputStream] or open the
  * file for random access operations using [open].
  */
 interface File default _File {
   /**
    * Create a File object.
    */
   File(String name);
 
   /**
+   * Create a File object from a Path object.
+   */
+  File.fromPath(Path path);
+
+  /**
    * Check if the file exists. Does not block and returns a
    * [:Future<bool>:].
    */
   Future<bool> exists();
 
   /**
    * Synchronously check if the file exists.
    */
   bool existsSync();
 
@@ skipping 339 matching lines @@
         sb.add(" ($osError)");
       }
     } else if (osError != null) {
       sb.add(": osError");
     }
     return sb.toString();
   }
   final String message;
   final OSError osError;
 }