Remove default onData for transformByHandlers (dart-lang/stream_transform#187)

Towards dart-lang/stream_transform#111

The default callback is not used in practice outside of tests, but it
included a cast to satisfy the type signature which looks worrying for
this type of library.

Make the callback required and add explicit callbacks (without a cast
since the types are consistent) in the tests which used it.
2 files changed
tree: a894727f79ebbbf95ebdc113016cac9008e8a0df
  1. pkgs/