Changed to use JSInterop

tools/dom/templates/html/impl/impl_Window.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;
 
 @DocsEditable()
 $if DART2JS
 $(ANNOTATIONS)@Native("Window,DOMWindow")
 $(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
@@ skipping 278 matching lines @@
    * (https://developer.mozilla.org/en-US/docs/Web/API/Window.scrollY) from MDN.
    */
   @DomName('Window.scrollY')
   @DocsEditable()
   int get scrollY => JS('bool', '("scrollY" in #)', this) ?
       JS('num', '#.scrollY', this).round() :
       document.documentElement.scrollTop;
 $else
   @DomName('Window.pageXOffset')
   @DocsEditable()
-  int get pageXOffset => _blink.BlinkWindow.instance.pageXOffset_Getter_(this).round();
+  int get pageXOffset => _blink.BlinkWindow.instance.pageXOffset_Getter_(unwrap_jso(this)).round();
 
   @DomName('Window.pageYOffset')
   @DocsEditable()
-  int get pageYOffset => _blink.BlinkWindow.instance.pageYOffset_Getter_(this).round();
+  int get pageYOffset => _blink.BlinkWindow.instance.pageYOffset_Getter_(unwrap_jso(this)).round();
 
   @DomName('Window.scrollX')
   @DocsEditable()
-  int get scrollX => _blink.BlinkWindow.instance.scrollX_Getter_(this).round();
+  int get scrollX => _blink.BlinkWindow.instance.scrollX_Getter_(unwrap_jso(this)).round();
 
   @DomName('Window.scrollY')
   @DocsEditable()
-  int get scrollY => _blink.BlinkWindow.instance.scrollY_Getter_(this).round();
+  int get scrollY => _blink.BlinkWindow.instance.scrollY_Getter_(unwrap_jso(this)).round();
 $endif
 }
 
 $if DART2JS
 class _BeforeUnloadEvent extends _WrappedEvent implements BeforeUnloadEvent {
   String _returnValue;
 
   _BeforeUnloadEvent(Event base): super(base);
 
   String get returnValue => _returnValue;
@@ skipping 38 matching lines @@
 
   ElementStream<BeforeUnloadEvent> forElement(Element e, {bool useCapture: false}) {
     return new _ElementEventStreamImpl(e, _eventType, useCapture);
   }
 
   ElementStream<BeforeUnloadEvent> _forElementList(ElementList e,
       {bool useCapture: false}) {
     return new _ElementListEventStreamImpl(e, _eventType, useCapture);
   }
 }