According to http://www.w3.org/TR/wai-aria-implementation/#mapping_state-property aria-flowto can be exposed as ATK_RELATION_FLOWS_TO.
<rdar://problem/15858584>
Created attachment 221658 [details] patch
Comment on attachment 221658 [details] patch LGTM
Comment on attachment 221658 [details] patch Clearing flags on attachment: 221658 Committed r162429: <http://trac.webkit.org/changeset/162429>
All reviewed patches have been landed. Closing bug.