Revert change 11459 and 11464.

lib/dom/templates/html/dart2js/factoryprovider_FormData.darttemplate

Index: lib/dom/templates/html/dart2js/factoryprovider_FormData.darttemplate
===================================================================
--- lib/dom/templates/html/dart2js/factoryprovider_FormData.darttemplate	(revision 11465)
+++ lib/dom/templates/html/dart2js/factoryprovider_FormData.darttemplate	(working copy)
@@ -1,10 +0,0 @@
-// 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.
-
-class $FACTORYPROVIDER {
-  factory FormData([FormElement form = null]) native '''
-    if (form == null) return new FormData();
-    return new FormData(form);
-  ''';
-}