[giow] (2) autofill: Encourage password saving.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=25879
Affected topics: HTML

git-svn-id: https://svn.whatwg.org/webapps@8794 340c8d12-0b0e-0410-8428-c7bf67bfef74