Consolidating all issues auto-filed by the flake detector into this one. As of this writing, this issue is mostly tracking dart-lang/test#1104 as the suspected culprit.

In short, the issue seems to be that the test runner first "loads" the test, then "runs" the test. However, the timeout clock starts when it loads the test. Since the concurrency level is limited (and because Flutter takes screenshots, has to be set to 1), by the time it's the test's turn to run it's well into the 12-minute timeout limit, so it times out. The fix should be to only start the clock when the test starts running. The correct thing to do would be to count the time between "load" and "run" as zero. More details in the Dart issue.

Relevant Google-internal issue: b/294950828