Switch dart:html objects not to be NativeFieldWrapper subclasses with JsInterop

tools/dom/scripts/systemhtml.py

Index: tools/dom/scripts/systemhtml.py
diff --git a/tools/dom/scripts/systemhtml.py b/tools/dom/scripts/systemhtml.py
index 222d8b1b1616ebe8ab06ec7ffe4c0dc821ca58d6..226eed1e587668a68527659903135933add25666 100644
--- a/tools/dom/scripts/systemhtml.py
+++ b/tools/dom/scripts/systemhtml.py
@@ -568,7 +568,7 @@ class HtmlDartInterfaceGenerator(object):
       elif (base_class == 'NativeFieldWrapperClass2' and
             self._options.dart_js_interop and
             not(isinstance(self._backend, Dart2JSBackend))):
-        base_class = 'JsoNativeFieldWrapper'
+        base_class = 'DartHtmlDomObject'
 
     annotations = self._metadata.GetFormattedMetadata(
         self._library_name, self._interface, None, '')
@@ -620,14 +620,12 @@ class HtmlDartInterfaceGenerator(object):
   {0}.internal_() : super.internal_();
 
 '''.format(class_name)
-    if base_class == 'NativeFieldWrapperClass2' or base_class == 'JsoNativeFieldWrapper':
+    if base_class == 'NativeFieldWrapperClass2' or base_class == 'DartHtmlDomObject':
         js_interop_wrapper = '''
   static {0} internalCreate{0}() {{
     return new {0}._internalWrap();
   }}
 
-  js.JsObject blink_jsObject;
-
   factory {0}._internalWrap() {{
     return new {0}.internal_();
   }}
@@ -642,7 +640,7 @@ class HtmlDartInterfaceGenerator(object):
             self._options.dart_js_interop and
             (self._interface.id == 'NamedNodeMap' or
              self._interface.id == 'CSSStyleDeclaration')):
-            base_class = 'JsoNativeFieldWrapper'
+            base_class = 'DartHtmlDomObject'
 
     implementation_members_emitter = implementation_emitter.Emit(
         self._backend.ImplementationTemplate(),