http://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/custom/index.html
This should probably have a webkit-dev feature discussion before moving forward.
(In reply to comment #1) > This should probably have a webkit-dev feature discussion before moving forward. Definitely! I'm under investing implementation side problem at bug 100229. Will start discussion once it gets better shape.
This implementation effort has been staled since Google forked Blink and the old implementation was subsequently removed. New implementation effort will be tracked separately.