[giow] (1) Make BroadcastChannel objects work in workers
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=24414
Affected topics: DOM APIs

git-svn-id: http://svn.whatwg.org/webapps@8660 340c8d12-0b0e-0410-8428-c7bf67bfef74
[giow] (0) Add BroadcastChannel.close()
Affected topics: DOM APIs

git-svn-id: http://svn.whatwg.org/webapps@8661 340c8d12-0b0e-0410-8428-c7bf67bfef74