The issue

The 3.29 candidate 0 stable branch has consistent Mac_mokey test failures: https://flutter-dashboard.appspot.com/#/build?repo=flutter&branch=flutter-3.29-candidate.0.

Previous to commit 7253c79 (which seems unrelated), the tests were failing with:

[/opt/s/w/ir/x/w/rc/tmp1hb8thed/flutter sdk/bin/cache/dart-sdk-darwin-x64.zip]
  End-of-central-directory signature not found.  Either this file is not
  a zipfile, or it constitutes one disk of a multi-part archive.  In the
  latter case the central directory and zipfile comment will be found on
  the last disk(s) of this archive.
unzip:  cannot find zipfile directory in one of /opt/s/w/ir/x/w/rc/tmp1hb8thed/flutter sdk/bin/cache/dart-sdk-darwin-x64.zip or
        /opt/s/w/ir/x/w/rc/tmp1hb8thed/flutter sdk/bin/cache/dart-sdk-darwin-x64.zip.zip, and cannot find /opt/s/w/ir/x/w/rc/tmp1hb8thed/flutter sdk/bin/cache/dart-sdk-darwin-x64.zip.ZIP, period.

It appears that the downloaded file is corrupt; please try again.

After the commit, the runs have been super short (~20 s) with an infra failure before the tests even begin to run:

Error in build protocol: Expected a terminal build status, got STARTED, while top level status is STARTED.

The cause needs to be identified to unblock the Flutter stable 3.29.1 release.

What we know

1. There were some potential culprits that we have ruled out:

• Skip Xcode install on mac_mokey Android tests #163685 (changes not present in flutter_3.29_candidate.0 branch).
• https://flutter-review.googlesource.com/c/recipes/+/62500 (changes not present in flutter_3.29_candidate.0 branch; self.skip set to false by default)

2. The 3.29.0 stable release did not have a clean postsubmit run either: https://flutter-dashboard.appspot.com/#/build?repo=flutter&branch=flutter-3.29-candidate.0&showBringup=true&hashFilter=35c388afb57ef061d06a39b537336c87e0e3d1b1. If we look at the Linux_release builder for this release, we see it actually timed out: https://ci.chromium.org/ui/p/dart-internal/builders/flutter/Linux%20flutter_release_builder/763/overview. Looking into related builds, it seems that the build documentation step of https://ci.chromium.org/ui/p/dart-internal/builders/flutter/Linux%20Production%20Engine%20Drone/43595/overview failed; not sure if that's related since that build itself only ran for ~15 minutes.