Implementing Alt-key underlines on menu headers in lo-menubar

Hi, I'm Ken Clive, and I'm attempting to fix the following bug in Ubuntu:

https://bugs.launchpad.net/ubuntu/+source/libreoffice/+bug/739184

Basically, I am trying to implement Alt shortcuts and underline the
appropriate letters in the menu headers (File, Edit, etc.) for the
lo-menubar package.  The items under each menu already have this
implemented, but the headers don't.  While this is a Unity-related
issue, I have been going through the libreoffice source code lately
and have not been able to find where the menus have been implemented
in the upstream builds.

I would like to find the appropriate libreoffice code because the
upstream has this feature implemented for the menu headers already,
and I plan to port this functionality over to fix this lo-menubar bug.
 All assistance is appreciated, thanks!

- Ken Clive.