Changed to use JSInterop

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

Index: tools/dom/templates/html/impl/impl_Window.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_Window.darttemplate b/tools/dom/templates/html/impl/impl_Window.darttemplate
index 81ee2b1b29856b60fdf1fcf52a18b4f0b29351a4..b119a08ea3bd85b3b5d551054abe0f64149dedf8 100644
--- a/tools/dom/templates/html/impl/impl_Window.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Window.darttemplate
@@ -296,19 +296,19 @@ $if DART2JS
 $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
 }