FileList is a sequence - make it have indexer.

lib/dom/dom.dart

 #library('dom');
 
 // 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.
 
 // DO NOT EDIT
 // Auto-generated Dart DOM library with no implementation.
 
 
@@ skipping 2930 matching lines @@
   final String name;
 
   String toString();
 }
 // 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.
 
 // WARNING: Do not edit - generated code.
 
-interface FileList {
+interface FileList extends List<File> {
 
   final int length;
 
   File item(int index);
 }
 // 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.
 
 // WARNING: Do not edit - generated code.
@@ skipping 9950 matching lines @@
 // 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.
 
 Window get window() => _dummy();
 
 // TODO(vsm): Remove when prefixes are supported.
 Window get dom_window() => _dummy();
 
 Document get document() => _dummy();