Migrate dom tests to dart:html.

client/tests/client/dom/CrossFrameTest.dart

 #library('CrossFrameTest');
 #import('../../../../lib/unittest/unittest.dart');
-#import('../../../../lib/unittest/dom_config.dart');
-#import('dart:dom');
+#import('../../../../lib/unittest/html_config.dart');
+#import('dart:html');
 
 main() {
-  useDomConfiguration();
+  useHtmlConfiguration();
 
   test('contentWindow', () {
-      final iframe = document.createElement('iframe');
-      document.body.appendChild(iframe);
+      final iframe = new Element.tag('iframe');
+      document.body.nodes.add(iframe);
       final frameWindow = iframe.contentWindow;
 
-      // Test this field to ensure a valid Dart wrapper.
-      Expect.isNull(frameWindow.dartObjectLocalStorage);
-
       // Ensure that the frame's document is inaccessible via window.
       Expect.throws(() => frameWindow.document);
     });
 
   test('contentDocument', () {
-      final iframe = document.createElement('iframe');
-      document.body.appendChild(iframe);
+      final iframe = new Element.tag('iframe');
+      document.body.nodes.add(iframe);
 
       // Ensure that the frame's document is inaccessible.
       Expect.throws(() => iframe.contentDocument);
     });
 }