for listboxes in WB_DROPDOWN mode which means the dropdown exists,
but when the drop down is not activated.

I think it's plausible that there was confusion around "b_IsDropDownList" and
that the meaning taken by the author was the the dropdown is active if
b_IsDropDownList is set, so renamed that to bHasDropDownList and take the old
"b_IsDropDownList" path when "b_IsDropDownList && ..IsInDropDown()"

Folded the then both equal code paths of the LISTBOX code together. No idea if
there should be an additional equivalent AccessibleEventId::SELECTION_CHANGED
for LISTBOXES like COMBOBOX instead of
AccessibleEventId::ACTIVE_DESCENDANT_CHANGED in the dropdown not active case.

Change-Id: I6db3ec21b392b7bf1b488235464202bb326f2535