HashMap grew by 8 bytes in rust-lang/rust#38368. script::dom::event_target::EventTarget contains:

    handlers: DOMRefCell<HashMap<Atom, EventListeners, BuildHasherDefault<FnvHasher>>>,

and DOM nodes contain EventTarget, so they all grew by the same amount, and unit tests in tests/unit/script/size_of.rs fail when updating the compiler: #15565 (comment)

@jdm @Ms2ger @nox What do you think? Should we take the hit and increase the expect size in unit tests, or try to get this space back somehow?