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

tools/dom/templates/html/impl/impl_MessageEvent.darttemplate

 // Copyright (c) 2013, 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.
 
 // WARNING: Do not edit - generated code.
 
 part of $LIBRARYNAME;
 
 $(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
   factory $CLASSNAME(String type,
@@ skipping 17 matching lines @@
     return event;
   }
 
 $if DARTIUM
   // TODO(alanknight): This really should be generated by the
   // _OutputConversion in the systemnative.py script, but that doesn't
   // use those conversions right now, so do this as a one-off.
   @DomName('MessageEvent.data')
   @DocsEditable()
   dynamic get data => convertNativeToDart_SerializedScriptValue(
-      _blink.BlinkMessageEvent.instance.data_Getter_(unwrap_jso(this)));
+      _blink.BlinkMessageEvent.instance.data_Getter_(this));
 
 $else
   // TODO(alanknight): This really should be generated by the
   // _OutputConversion in the systemnative.py script, but that doesn't
   // use those conversions right now, so do this as a one-off.
   @DomName('MessageEvent.data')
   @DocsEditable()
   dynamic get data => convertNativeToDart_SerializedScriptValue(this._get_data);
 
   @JSName('data')
   @DomName('MessageEvent.data')
   @DocsEditable()
   @annotation_Creates_SerializedScriptValue
   @annotation_Returns_SerializedScriptValue
   final dynamic _get_data;
 
 $endif
 
 $!MEMBERS
 }