Fine. Update expectations printer before changes to the implementation.

Split of https://dart-review.googlesource.com/c/sdk/+/445346 PS3.

Change-Id: Iaaa3df38e990fc3bd3940d2f255d4eccf15b3f20
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/445525
Reviewed-by: Paul Berry <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov