Optimize dartium dart:html bindings so real world application performance is acceptable. Improves d…

tools/dom/templates/html/impl/impl_XMLHttpRequest.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.
 
 part of $LIBRARYNAME;
 
  /**
   * A client-side XHR request for getting data from a URL,
   * formally known as XMLHttpRequest.
   *
@@ skipping 386 matching lines @@
    * Note: Most simple HTTP requests can be accomplished using the [getString],
    * [request], [requestCrossOrigin], or [postFormData] methods. Use of this
    * `open` method is intended only for more complext HTTP requests where
    * finer-grained control is needed.
    */
   @DomName('XMLHttpRequest.open')
   @DocsEditable()
 $if JSINTEROP
   void open(String method, String url, {bool async, String user, String password}) {
     if (async == null && user == null && password == null) {
-      _blink.BlinkXMLHttpRequest.instance.open_Callback_2_(unwrap_jso(this), method, url);
+      _blink.BlinkXMLHttpRequest.instance.open_Callback_2_(this, method, url);
     } else {
-      _blink.BlinkXMLHttpRequest.instance.open_Callback_5_(unwrap_jso(this), method, url, async, user, password);
+      _blink.BlinkXMLHttpRequest.instance.open_Callback_5_(this, method, url, async, user, password);
     }
   }
 $else
   void open(String method, String url, {bool async, String user, String password}) native;
 $endif
 
 $!MEMBERS
 }