use .append instead of .nodes.add

tests/html/postmessage_structured_test.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
 
 library postmessage_js_test;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_individual_config.dart';
 import 'dart:html';
 import 'dart:collection';  // SplayTreeMap
 import 'dart:typed_data';
 import 'utils.dart';
 
 injectSource(code) {
   final script = new ScriptElement();
   script.type = 'text/javascript';
   script.innerHtml = code;
-  document.body.nodes.add(script);
+  document.body.append(script);
 }
 
 main() {
   useHtmlIndividualConfiguration();
 
   go(testName, value) =>
       test(testName, () {
           // Round-trip graph from Dart to JavaScript and back.
 
           final JS_CODE = """
@@ skipping 115 matching lines @@
     var typed_arrays_list = [view_a, array_buffer, view_b];
 
     // Note that FF is failing this test because in the sent message:
     // view_a.buffer == array_buffer
     // But in the response:
     // view_a.buffer != array_buffer
     go('typed_arrays_list', typed_arrays_list);
   });
 
 }