Steps to reproduce:

1. Launch Writer and Accerciser

2. Turn event monitoring on in Accerciser

3. In Writer, cause a toolbar tooltip to appear either by hovering the mouse
over a button or by moving focus to it and pressing Ctrl+F1

Expected results: An object:state-changed:showing event (detail1 == 1) would be
emitted.

Actual results: An object:state-changed:showing event is not emitted, though we
do get an object:state-changed:visible (detail1 == 1) event.

Impact: All of the other toolkits and applications (that I am aware of) which
expose tooltips via at-spi, emit an object:state-changed:showing event. Orca at
the moment does not listen for object:state-changed:visible events -- and it
won't until we've been able to ascertain that doing so will not impact
performance across the board.

Therefore, what I am hoping is that it will be quite easy for you to emit this
event at the same time you emit the object:state-changed:visible event. If so,
things should JustWork(tm). If it's more difficult than that, please let me know
and I'll start doing performance analysis. Thanks in advance!