Perhaps a ":host" pseudoclass? How will this work with multiple shadow trees?
The gist of the problem:
* If we allow addressing shadow host in scoped stylesheets in shadow DOM subtree, we are creating a situation where some rules would step outside of the shadow DOM subtree, thus making things rather confusing.
* If we don't allow this, we have no way to style a shadow host from a shadow DOM subtree.
At this point, I think the latter is less evil than the former and pick it.
Need to modify the rule applicability algorithm to allow rules with certain selectors to be applicable in the document.
Tab, is ":host" a good name? Anything I can crib from Selectors 4?
Going with ":host". Loook out! :P