[giow] (1) Make sure <style> does nothing when there's no browsing context.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=26144
Affected topics: HTML

git-svn-id: http://svn.whatwg.org/webapps@8729 340c8d12-0b0e-0410-8428-c7bf67bfef74