`Mac module_test_ios` is flaky (2.41%) due to FlutterUITests failures

[LongCatIsLooong]

2 most recent failures:

https://ci.chromium.org/ui/p/flutter/builders/prod/Mac%20module_test_ios/3264/overview
Error message:

FlutterUITests/FlutterUITests.m:91: error: -[FlutterUITests testDualCold] : (([app.staticTexts matchingType:XCUIElementTypeStaticText identifier:@"This is Marquee"].count) equal to (2)) failed: ("1") is not equal to ("2")

https://ci.chromium.org/ui/p/flutter/builders/prod/Mac%20module_test_ios/3254/overview
Error message:

FlutterUITests/FlutterUITests.m:52: error: -[FlutterUITests testFlutterViewWarm] : (([app.staticTexts[@"Button tapped 0 times."] waitForExistenceWithTimeout:60.0]) is true) failed

[jmagman]

At least for the first case, it looks like the test found the native "This is Marquee" but didn't wait enough time for the Flutter view to show it.

  Assertions: Assertion Failure at FlutterUITests.m:91: (([app.staticTexts matchingType:XCUIElementTypeStaticText identifier:@"This is Marquee"].count) equal to (2)) failed: ("1") is not equal to ("2")
  File: FlutterUITests.m:91

[jmagman]

I think in both cases elements are being verified before being awaited. Assigning to me.

[bdero]

Ran into a similar timeout for testFlutterViewWarm on the engine roll recently: https://ci.chromium.org/ui/p/flutter/builders/try/Mac%20module_test_ios/8289/overview