This is a page from the Cascading Style Sheets Working Group Blog. Some other places to find information are the “current work” page, the www-style mailing list, the Future of CSS syndicator, and the issue list on Github.
Do you want to know how the CSS WG works? Fantasai has written about:csswg, An Inside View of the CSS Working Group at W3C.
-webkit-device-pixel-ratio
should be defined in the Media Queries spec. Several people had no wish to define it since it’s an alias to the resolution media query, but there was concern that that’s compatibility hostile since currently you need -webkit-device-pixel-ratio
to be web compatible.