[giow] (2) Fire 'change' when unselected a video track too.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=26095
Affected topics: Video and Audio

git-svn-id: http://svn.whatwg.org/webapps@8723 340c8d12-0b0e-0410-8428-c7bf67bfef74