Revert "Remove unnecessary import" (dart-lang/stream_channel#71)

This reverts commit f2dcd319ec1efca9d01abd5500436e2cb63e4c53.

Since this has not been published or rolled through to the SDK or
Flutter we will hold it back to reduce risk.
1 file changed
tree: 4d55e3fe9cf1ea7834d06bdf6b477f56b164c7ab
  1. pkgs/