Is text/xml-script working ?

XML-script has been moved to Preview component. You have to add reference to Microsoft.Web.Preview.dll and add scriptmanager as followed:

<asp:ScriptManager ID="TheScriptManager" runat="server">
           <Scripts>
               <asp:ScriptReference Assembly="Microsoft.Web.Preview"
 Name="PreviewScript.js" />
           </Scripts>
</asp:ScriptManager>