style: Hook the use counters into StyleSheet parsing.

Still not hooked into telemetry, I talked with :janerik and :gfritzsche about
that, but test incoming!

This intentionally doesn't handle CSSOM and such for now, will file followups
for those, though should be trivial.

I want to unify / clean up how we do the use counters and the error reporting
stuff for CSSOM, since the current function call still shows up in profiles,
but that should be a follow-up.

Differential Revision: https://phabricator.services.mozilla.com/D3828

components/style/stylesheets/keyframes_rule.rs

@@ -219,6 +219,7 @@ impl Keyframe {
             ParsingMode::DEFAULT,
             parent_stylesheet_contents.quirks_mode,
             None,
+            None,
         );
         context.namespaces = Some(&*namespaces);
         let mut input = ParserInput::new(css);