[giow] (1) Update the spec to say what's exposed to workers: take 1
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=22646
Affected topics: Canvas, DOM APIs, HTML, HTML Syntax and Parsing, Offline Web Applications, Workers

git-svn-id: http://svn.whatwg.org/webapps@8425 340c8d12-0b0e-0410-8428-c7bf67bfef74