<Swing Dev> RfR JDK-8145207 [macosx] JList, VO can't access non-visible list items

[Pete Brunet]

Please review the following patch.

Bug: https://bugs.openjdk.java.net/browse/JDK-8145207
Patch: http://cr.openjdk.java.net/~ptbrunet/JDK-8145207/webrev.00/

This fixes the following functionality that was not working with the
JList of ListDemo of SwingSet2.
- start VoiceOver
- start SwingSet2
- start the ListDemo
- press Tab until focus is on the list, should hear VO when changing
selections with up/down arrow
- when interacting with list should hear that there are 30 (total)
items, not 26 (visible) items
- when using control+option+up/downarrow should be able to move to and
select (control+option+spacebar) non-visible items past the 26th visible
item
- should be able to multi-select both visible and invisible items using
control+option+command+return and VO should read the item just added
- should be able to shift extend items with shift up or shift down arrow
and VO should announce the item just added or removed

Pete