While investigating <rdar://problem/9524530>, I discovered that the accessibility layer does not support performing a default action on list items. This prevents the list items from being 'selected' in the accessibility object tree, and prevents IAccessible clients from seeing that the list item has a default action associated with it. Generally, the default action will be like menu items or list box items (i.e., a "select" action).
Created attachment 205041 [details] Patch
Comment on attachment 205041 [details] Patch Attachment 205041 [details] did not pass efl-ews (efl): Output: http://webkit-queues.appspot.com/results/926354
Comment on attachment 205041 [details] Patch Attachment 205041 [details] did not pass efl-wk2-ews (efl-wk2): Output: http://webkit-queues.appspot.com/results/950657
Created attachment 205053 [details] Revised to prevent Gtk/EFL/Blackberry build errors.
Committed r151778: <http://trac.webkit.org/changeset/151778>