update elements and fix some bugs

test/iron_form_test.dart

Index: test/iron_form_test.dart
diff --git a/test/iron_form_test.dart b/test/iron_form_test.dart
index 098bf1a90335be0cf505875d5691b69955cda5ff..a8b3e9e072430ed33b763cbc951150b919a76b68 100644
--- a/test/iron_form_test.dart
+++ b/test/iron_form_test.dart
@@ -187,7 +187,7 @@ main() async {
       form.on['iron-form-response'].take(1).listen((event) {
         expect(submitted, isTrue);
 
-        var response = new JsObject.fromBrowserObject(event)['detail'];
+        var response = convertToDart(event).detail.response;
         expect(response, isNotNull);
         expect(response is JsObject, isTrue);
         expect(response['success'], isTrue);
@@ -209,7 +209,7 @@ main() async {
 
       form.on['iron-form-response'].take(1).listen((event) {
         expect(submitted, isTrue);
-        var response = event.detail;
+        var response = convertToDart(event).detail.response;
         expect(response, isNotNull);
         expect(response is JsObject, isTrue);
         expect(response['success'], isTrue);