更多的查询 & bugs

• https://stackoverflow.com/questions/44564366/inheritance-inside-a-shadow-dom-slot
• https://github.com/w3c/csswg-drafts/issues/1535
• https://github.com/w3c/csswg-drafts/issues/1530
• https://twitter.com/praveenpuglia/status/876677801146896384