Webkit purposefully does not send live region notifications if some client has not accessed the AX tree in between the last live region update (ostensibly to improve performance) However, this is problematic because if a screen reader misses one notification it has no idea what happened and the only recourse is to rescan the page for changes. I believe the correct thing to do is to always send notifications.
Created attachment 110855 [details] patch
rdar://10276628
http://trac.webkit.org/changeset/97627