use .append instead of .nodes.add

tests/html/native_gc_test.dart

 library NativeGCTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 
 var testEvent = new EventStreamProvider<Event>('test');
 
 main() {
   useHtmlConfiguration();
 
@@ skipping 20 matching lines @@
 
       final event = new Event('test');
       div.dispatchEvent(event);
   });
 
   test('WindowEventListener', () {
     String message = 'WindowEventListenerTestPingMessage';
 
     Element testDiv = new DivElement();
     testDiv.id = '#TestDiv';
-    document.body.nodes.add(testDiv);
+    document.body.append(testDiv);
     window.onMessage.listen((e) {
       if (e.data == message) testDiv.click();
     });
 
     for (int i = 0; i < 100; ++i) {
       triggerMajorGC();
     }
 
     testDiv.onClick.listen(expectAsync1((e) {}));
     window.postMessage(message, '*');
   });
 }
 
 void triggerMajorGC() {
   List list = new List(1000000);
   Element div = new DivElement();
   div.onClick.listen((e) => print(list[0]));
 }