Encapsulating CSS in Shadow DOM

I am hoping it will be possible to have root em like font size based
values, but based on the shadow root (or host) when using shadow dom. Like
10hem (host em) or something like that. That would make it a lot easier to
make scalable widgets/components where only one or a few css properties
would have to be changed when scaling the content in different contexts.

I have described this in more detail here:

http://stackoverflow.com/questions/24953647/font-size-css-values-based-on-shadow-dom-root