The first time I mentioned the need to reach the internal CSS parser of a rendering engine from JavaScript was 17 years ago during the CSS WG meeting I hosted at 'Electricit'e de France in 1998, during a corridor discussion. All the people around said it was out of question. Then I put it back on the table in 2002, with little success again. Today, I was actioned by the CSS WG and the TAG in the Houdini Task Force to start editing a new document (with Tab Atkins, Shane Stevens and Brian Kardell) called CSS Parser and Tokenizer API. It does not say it's going to be accepted or anything, but at least it went beyond the 5 minutes chat and rebuttal. I am extremely happy and proud If we succeed making it happen, this is going to be a game-changer for a lot of web applications!!!

http://www.glazman.org/weblog/dotclear/index.php?post/2015/02/08/CSS-Parser-and-Tokenizer-API