[agiow] (0) Add reportValidity(), which is like checkValidity() but triggers the browser's error-reporting UI as well
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=17826
Affected topics: DOM APIs, HTML

git-svn-id: http://svn.whatwg.org/webapps@8210 340c8d12-0b0e-0410-8428-c7bf67bfef74