ACTION-1527: Investigate the proper uia mappings for aria-current

The best mapping is SelectionItem, which has a required property of SelectionContainer. This gets to the issue Joanie was discussing on the call about knowing what the container is. In UIA, we need to know.

I'm still not clear on what the difference is between current and selected. Before I can ask for new UIA patterns, I need a much better description of why selection isn't the right thing.

http://msdn.microsoft.com/en-us/library/windows/desktop/ee671286(v=vs.85).aspx

Note, I am not suggesting changing the control type/role of the object to selectionitem, but adding the selecitonitem pattern to the object, and the selection pattern to the container of the objects. To map this in UIA, we do need to know what the container is, as selectioncontainer is a required property for the selectionitem pattern

drat, selectionitem pattern can't be used on images. It looks like there is not a good mapping to UIA for this. Now the question is whether to update both ARIA and UIA to allow selection on any role/control type, or to try to get something like aria-current added to uia.

for 1.1, put it in the AriaProperties properties.

Edits complete, changelog is:
https://github.com/w3c/aria/commit/f719d85e4cf34aa372b994280bc11de6971f726b

See:
http://rawgit.com/w3c/aria/master/core-aam/core-aam.html#ariaCurrent

[joanie]: Closing based on consensus from the 10-Nov-2015 AAPI meeting.