[giow] (3) OnBeforeUnloadEventHandler is supposed to allow null return values (and some markup error fixes, oops)
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=23489
Affected topics: DOM APIs, Rendering

git-svn-id: http://svn.whatwg.org/webapps@8282 340c8d12-0b0e-0410-8428-c7bf67bfef74