Instead of using CanGc::note() in

, we should make it a method argument via .

This matters because it's called from

and we keep writing code that calls self.seek(..) within a borrow_mut(), which can trigger a panic if a GC occurs. We need to chain the CanGc arguments as far up the stack as possible!

No need to run any tests; if it compiles, that's good enough for a PR.