style: Parsing for relative selectors in :has()

Differential Revision: https://phabricator.services.mozilla.com/D171358

components/malloc_size_of/lib.rs

@@ -717,7 +717,8 @@ where
             Component::Scope |
             Component::ParentSelector |
             Component::Nth(..) |
-            Component::Host(None) => 0,
+            Component::Host(None) |
+            Component::RelativeSelectorAnchor => 0,
         }
     }
 }