With flutter/engine#41573, when FlutterClippingMaskViewPool is requested a mask view, it now randomly picks one from its pool. While this behavior is perfectly ok from the outside, it might cause false failure in certain unit tests that assume the result to be deterministic.

Error log: https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8780912233583277217/+/u/test:_Tests_for_ios_debug_sim/stdout?format=raw