The callback can be used to process the received data a single time, and
in that case this._updated should only be toggled after the callback has
completed, since other methods may depend on its side effects.
In other scenarios the order does not matter (either way).
According to warning given today with gnome 3.30:
"Some code called array.toString() on a Uint8Array instance. Previously this would have interpreted the bytes of the array as a string, but that is nonstandard. In the future this will return the bytes as comma-separated digits. For the time being, the old behavior has been preserved, but please fix your code anyway to explicitly call ByteArray.toString(array)."
