Support for the Call Hierarchy toolwindow in VS2012

Hi,

I have a custom language service and I would like to support the Call Hierarchy toolwindow.  There are references in the MSDN documentation to several interfaces from Microsoft.VisualStudio.Language.CallHierarchy but nothing on registering a data provider.

"Represents a callback that the UI gives to the data provider during a search."

http://msdn.microsoft.com/en-ca/library/microsoft.visualstudio.language.callhierarchy.icallhierarchysearchcallback.aspx

If this scenario is not supported in VS2012, is it available/planned for VS2013?

Regards,

-Martin