9faca2fa68
Strengthen requirement on `label` to match Fuchsia. Change-Id: Iebc9e0cc7be5984ad2b94dde561b76aec64fe78a Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/96145 Reviewed-by: Chinmay Garde <chinmaygarde@google.com> Commit-Queue: Ryan Macnak <rmacnak@google.com>