use .append instead of .nodes.add

tests/html/shadow_dom_test.dart

Index: tests/html/shadow_dom_test.dart
diff --git a/tests/html/shadow_dom_test.dart b/tests/html/shadow_dom_test.dart
index 7f6112ee28be54f94a0b445d203c6732b05f141b..78b62b5e6583b2f2158593e48ad6e960a4901b80 100644
--- a/tests/html/shadow_dom_test.dart
+++ b/tests/html/shadow_dom_test.dart
@@ -28,11 +28,11 @@ main() {
       div2 = new DivElement();
       div1.classes.add('foo');
       shadowRoot = div2.createShadowRoot();
-      shadowRoot.nodes.add(paragraph1);
-      shadowRoot.nodes.add(new ContentElement());
-      div2.nodes.add(paragraph2);
-      document.body.nodes.add(div1);
-      document.body.nodes.add(div2);
+      shadowRoot.append(paragraph1);
+      shadowRoot.append(new ContentElement());
+      div2.append(paragraph2);
+      document.body.append(div1);
+      document.body.append(div2);
     }
 
     var expectation = ShadowRoot.supported ? returnsNormally : throws;