137c7b6c84
This prepares front_end unittests for turning on non-nullable by default. Change-Id: I9588a2d026ab9f5b1dcf08a140d25bd5dca3d5bd Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/168346 Reviewed-by: Jens Johansen <jensj@google.com> Commit-Queue: Johnni Winther <johnniwinther@google.com>