Fixup for https://phabricator.services.mozilla.com/D259803

Signed-off-by: Oriol Brufau <[email protected]>

Author: Loirooriol

style/properties/properties.mako.rs

@@ -2004,6 +2004,7 @@ impl ComputedValues {
             PropertyDeclarationId::Longhand(id) => {
                 let context = resolved::Context {
                     style: self,
+                    for_property: id.into(),
                 };
                 let mut s = String::new();
                 self.computed_or_resolved_value(