[giowt] (0) Make inert='' map to aria-hidden rathe than aria-disabled since aria-disabled only really does anything with interactive content.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=23350
Affected topics: HTML

git-svn-id: http://svn.whatwg.org/webapps@8209 340c8d12-0b0e-0410-8428-c7bf67bfef74