ARIA computation algorithm says to always fallback to the host language "tooltip" attribute (WebKit does not use @title as the label on IMG), but I think an explicitly empty alt attribute should override that on img. I've added a test case.
2. D. "The last resort is to use text from a tooltip attribute (such as the title attribute in HTML). This is used only if nothing else, including subtree content, has provided results."
Created attachment 197889 [details]
test case demonstrating bug
See also: bug 112842.
Created attachment 198136 [details]
Adding Tim to help with review
Comment on attachment 198136 [details]
Clearing flags on attachment: 198136
Committed r148617: <http://trac.webkit.org/changeset/148617>
All reviewed patches have been landed. Closing bug.