AX: support aria-posinset, aria-setsize for radio buttons

• Component: Accessibility
• Status: NEW ---

[Aaron Leventhal]

Example with <input type="radio">:
data:text/html,<div role="radigroup"><label><input type="radio" name="z" aria-posinset="50" aria-setsize="60">Cats</label><label><input type="radio"name="z"  aria-posinset="51" aria-setsize="60">Dogs</label></div>

Example using ARIA role=radio:
data:text/html,<div role="radiogroup"><div tabindex="0" role="radio" aria-posinset="20" aria-setsize="30">Fish</div><div tabindex="0" role="radio" aria-posinset="21" aria-setsize="30">Bird</div></div>

Steps:
1. Run one of the above examples with VoiceOver and Safari
2. Tab through the items
Notice that that items are read as "1 of 2" and "2 of 2", not respecting the ARIA positional markup.

See also bug 98202 for list items.
http://www.w3.org/TR/wai-aria/states_and_properties#aria-posinset
http://www.w3.org/TR/wai-aria/states_and_properties#aria-setsize

[Radar WebKit Bug Importer]

<rdar://problem/83947714>

[Aaron Leventhal]

Also, when AXARIAPosInSet/AXARIASetSize are used on a radio, it would be great if a radiogroup object is not required as a parent, because it is possible to use radio buttons without a radiogroup ancestor.