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

tools/dom/templates/html/dartium/html_dartium.darttemplate

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // DO NOT EDIT
 // Auto-generated dart:html library.
 
 /**
  * HTML elements and other resources for web-based applications that need to
  * interact with the browser and the DOM (Document Object Model).
@@ skipping 343 matching lines @@
 // List of known tagName to DartClass for custom elements, used for upgrade.
 var _knownCustomeElements = new Map<String, Type>();
 
 Rectangle make_dart_rectangle(r) =>
     r == null ? null : new Rectangle(
     js.JsNative.getProperty(r, 'left'),
     js.JsNative.getProperty(r, 'top'),
     js.JsNative.getProperty(r, 'width'),
     js.JsNative.getProperty(r, 'height'));
 
-// Need a default constructor for constructing classes with mixins that are
-// also extending NativeFieldWrapperClass2.  Defining JsoNativeFieldWrapper
-// extending NativeFieldWrapperClass2 creates a default constructor.
-class JsoNativeFieldWrapper extends NativeFieldWrapperClass2 {}
+/// An abstract class for all DOM objects we wrap in dart:html and related
+///  libraries.
+class DartHtmlDomObject {
+
+  /// The underlying JS DOM object.
+  js.JsObject blink_jsObject;
+
+}
 
 // Flag to disable JS interop asserts.  Setting to false will speed up the
 // wrap_jso calls.
 bool __interop_checks = true;
 
 /** Expando for JsObject, used by every Dart class associated with a Javascript
  *  class (e.g., DOM, WebAudio, etc.).
  */
 
 /**
@@ skipping 301 matching lines @@
 createCustomUpgrader(Type customElementClass, $this) {
   var dartClass;
   try {
     dartClass = _blink.Blink_Utils.constructElement(customElementClass, $this);
   } catch (e) {
     dartClass.badUpgrade();
     throw e;
   } finally {
     // Need to remember the Dart class that was created for this custom so
     // return it and setup the blink_jsObject to the $this that we'll be working
-    // with as we talk to blink. 
+    // with as we talk to blink.
     js.setDartHtmlWrapperFor($this, dartClass);
   }
 
   return dartClass;
 }
 
 $else
-class JsoNativeFieldWrapper extends NativeFieldWrapperClass2 {}
+class DartHtmlDomObject extends NativeFieldWrapperClass2 {}
 
 unwrap_jso(dartClass_instance) => dartClass_instance;
 wrap_jso(jsObject) => jsObject;
 make_dart_rectangle(r) => r;
 convertDartToNative_Dictionary(Map dict) => dict;
 List convertDartToNative_StringArray(List<String> input) => input;
 convertDartToNative_List(List input) => input;
 createCustomUpgrader(Type customElementClass, $this) => $this;
 
 $endif