use .append instead of .nodes.add

tests/html/window_open_test.dart

 library WindowOpenTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 import 'dart:async';
 
 main() {
   useHtmlConfiguration();
   evaluateJavaScript(code) {
     final scriptTag = new Element.tag('script');
     scriptTag.innerHtml = code;
-    document.body.nodes.add(scriptTag);
+    document.body.append(scriptTag);
   }
   evaluateJavaScript('(testRunner || layoutTestController).setCanOpenWindows()');
 
   test('TwoArgumentVersion', () {
     Window win = window.open('../resources/pong.html', 'testWindow');
     closeWindow(win);
   });
   test('ThreeArgumentVersion', () {
     Window win = window.open("resources/pong.html", "testWindow", "scrollbars=yes,width=75,height=100");
     closeWindow(win);
   });
 }
 
 closeWindow(win) {
   win.close();
   doneHandler() {
     if (!win.closed) {
       new Timer(const Duration(milliseconds: 1), expectAsync0(doneHandler));
     }
   }
   new Timer(const Duration(milliseconds: 1), expectAsync0(doneHandler));
 }