* Update named configs for unit tests to Dart 2.
* Bump json_rpc_2 in front_end package.
* Use named configurations in unit tests.
* Fix typing issues.
Change-Id: Id3b393a0d2abe92c8eaec10fa8057fb35d18a4c6
Reviewed-on: https://dart-review.googlesource.com/67341
Reviewed-by: Jens Johansen <jensj@google.com>