The most recent Skia->engine and Dart->engine roll attempts failed due to timeouts in the "Mac Web Engine" builder on LUCI.

The "felt test safari desktop" step was killed after 54 minutes. The stdout log on LUCI only contained a Received SIGTERM. Shutting down. message.

See:
flutter/engine#27556
https://ci.chromium.org/p/flutter/builders/try/Mac%20Web%20Engine/18129