Node passes a stream's one onwrite function to every _write and _writev
call, and a new function to every _transform call. A write or writev
option callback now receives the same closure on every call
(scr_stream_write_closure), kept or not, so a Set, WeakSet or WeakMap
finds it again. A reused transform, flush, final, construct or destroy
callback is first forgotten by weak collections, as at its free, so a
WeakSet or WeakMap that recorded the previous call's callback does not
find it on the next call.
Chris Tate
7ae99f63bc