[giow] (3) align 'load' and 'unload' events since they have similar quirks in practice
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=25209
Affected topics: DOM APIs, HTML, HTML Syntax and Parsing

git-svn-id: http://svn.whatwg.org/webapps@8609 340c8d12-0b0e-0410-8428-c7bf67bfef74