Inline some typedefs (dart-lang/stream_transform#81)

In each place where these were used they matched the argument/field name
anyway so it was repetitive and the name was not adding useful
information. They were all a bit shorter than the function type, but not
so much so that it's worth the extra level of indirection.
1 file changed
tree: 9fc6e7e2d1177870e8491dc3021f66b65982cbf8
  1. pkgs/