Remove "Shadow DOM"

via https://github.com/w3c/webcomponents/commit/7aab02de080ac271e7400ed65c0f61dde694cceb
Remove "Web Components"
Add "Shadow DOM Styling"
Add "Non-element Selectors"
Remove ::region()

via https://dvcs.w3.org/hg/csswg/rev/2b9b7b8a9656
Add "CSSOM View"