Called by the framework when the user performs an action that discards the undo state while editing the OLE item.
The default implementation does nothing. Override this function if you are implementing the undo command in your container application. In your override, discard the container application's undo state.
If the server was written with the Microsoft Foundation Class Library, the server can cause this function to be called by calling COleServerDoc::DiscardUndoState.
For more information, see IOleInPlaceSite::DiscardUndoState in the Windows SDK.