This change makes test.dart handle if the baseline commit hasn't been built
on the requested builder and instead attempts to search for whether there's
results for up to 25 preceding commits, which it then uses as an inexact
baseline.
Closes https://github.com/dart-lang/sdk/issues/36211
Change-Id: Ie44042c67c9460826736f4a2cf159d8d7b455f0b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/96944
Reviewed-by: William Hesse <whesse@google.com>
Jonas Termansen
1c02016b7b