what a loader may use while it works: a signal that says the request was replaced, and a way to report how far along it is
aborted when a newer request for the same kind replaces this one, so a long render can stop early
the request being loaded, including the content id, engine and frame a restored save carries
reports progress from 0 to 1; AudioBus.onLoadProgress forwards it
AudioBus.onLoadProgress
what a loader may use while it works: a signal that says the request was replaced, and a way to report how far along it is