Making FormData able to add Blobs and Files.

sdk/lib/html/dartium/html_dartium.dart

 library html;
 
 import 'dart:collection';
 import 'dart:html_common';
 import 'dart:indexed_db';
 import 'dart:isolate';
 import 'dart:json';
 import 'dart:nativewrappers';
 import 'dart:svg' as svg;
 import 'dart:web_audio' as web_audio;
@@ skipping 10952 matching lines @@
   factory FormData([FormElement form]) {
     if (!?form) {
       return _FormDataFactoryProvider.createFormData();
     }
     return _FormDataFactoryProvider.createFormData(form);
   }
   FormData.internal();
 
 
   /** @domName DOMFormData.append */
-  void append(String name, String value, String filename) native "DOMFormData_append_Callback";
+  void append(String name, value, [String filename]) native "DOMFormData_append_Callback";
 
 }
 // 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.
 
 
 /// @domName HTMLFormElement
@@ skipping 18750 matching lines @@
   bool get isEmpty => Maps.isEmpty(this);
 }
 
 get _printClosure => (s) {
   try {
     window.console.log(s);
   } catch (_) {
     _Utils.print(s);
   }
 };