Ancestor hashes for the bloom filter. We precompute these and store them
inline with selectors to optimize cache performance during matching.
This matters a lot.
The properties that comprise an :nth- pseudoclass as of Selectors 4 (e.g.,
nth-child(An+B [of S]?)).
https://www.w3.org/TR/selectors-4/#nth-child-pseudo
The properties that comprise an :nth- pseudoclass as of Selectors 3 (e.g.,
nth-child(An+B)).
https://www.w3.org/TR/selectors-3/#nth-child-pseudo
Storage for a relative selector.
A Selector stores a sequence of simple selectors and combinators. The
iterator classes allow callers to iterate at either the raw sequence level or
at the level of sequences of simple selectors separated by combinators. Most
callers want the higher-level iterator.