Add `combineLatest` (dart-lang/stream_transform#65)

Closes dart-lang/stream_transform#63

Uses a manual `StreamTransformer` implementation based closely on the
`merge` implementation. This can't be implemented on top of
`fromHandlers` or normal stream methods because the events emitted
aren't triggered by a single source.
5 files changed
tree: 584cd582a5740303be6bd7e355ab6833a6cd04a0
  1. pkgs/