If my window hosts multiple windowless ActiveX controls, which one do I call IOleInPlaceActiveObject::TranslateAccelerator and IOleInPlaceObjectWindowless::OnWindowMessage on?

Commenter Farproc asks how one goes about hosting two windowless ActiveX controls in a single window. In particular, "none of the documentation explains how to choose which control to send and on?" Actually, the documentation does say. The documentation for says, "Active in-place objects must always be given the first chance at translating ac...