[giow] (3) The bulk of this is editorial: refactoring how scripts are defined so that all the common stuff is in a shared 'settings object' rather than being duplicated per script. But this also cleans up how postMessage() interacts with the event loop and a few other things I've since forgotten.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=22863
Affected topics: DOM APIs, HTML, HTML Syntax and Parsing, Rendering, Security, Workers

git-svn-id: http://svn.whatwg.org/webapps@8247 340c8d12-0b0e-0410-8428-c7bf67bfef74