[giow] (3) Update how the interaction with CSS style sheets and CSSOM is defined.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=14703
Affected topics: CSS, DOM APIs, HTML

git-svn-id: http://svn.whatwg.org/webapps@8390 340c8d12-0b0e-0410-8428-c7bf67bfef74