I think you'd want to deprecate at apply not parse time.
Elliott: I basically just followed the existing use counters in the
parser, added a few months ago (I forget who added them). Which
function would you put them in?
Philip: Sadly I can't add deprecation messages from CSSPropertyParser
(that's what I tried), because I don't have a LocalFrame object
available. Neither the CSSParserContext nor the UseCounter keep a
reference to it, and without it I don't have a console object
available to show the deprecation message. Unless I'm missing another
way to do it.
Yep - deprecation will ship in 47, removal in 48. Thanks!