[giow] (2) Block popups from some weird edge cases that fire 'change' events on <select> as a result of script.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=25504
Affected topics: HTML

git-svn-id: http://svn.whatwg.org/webapps@8720 340c8d12-0b0e-0410-8428-c7bf67bfef74