use .append instead of .nodes.add

tests/html/events_test.dart

 library EventsTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 
 main() {
   useHtmlConfiguration();
 
   test('TimeStamp', () {
     Event event = new Event('test');
@@ skipping 11 matching lines @@
       expect(e.bubbles, bubble, reason: 'canBubble was set to $bubble');
       expect(e.cancelable, cancel, reason: 'cancelable was set to $cancel');
     }
   });
 
   // The next test is not asynchronous because [on['test'].dispatch(event)] fires the event
   // and event listener synchronously.
   test('EventTarget', () {
     Element element = new Element.tag('test');
     element.id = 'eventtarget';
-    window.document.body.nodes.add(element);
+    window.document.body.append(element);
 
     int invocationCounter = 0;
     void handler(Event e) {
       expect(e.type, equals('test'));
       Element target = e.target;
       expect(element, equals(target));
       invocationCounter++;
     }
 
     Event event = new Event('test');
@@ skipping 23 matching lines @@
     invocationCounter = 0;
     element.dispatchEvent(event);
     expect(invocationCounter, 1);
   });
 
   test('InitMouseEvent', () {
     DivElement div = new Element.tag('div');
     MouseEvent event = new MouseEvent('zebra', relatedTarget: div);
   });
 }