Reduce real-timing test flakiness
Reduce real-timing test flakiness

Marginally reduce the flakiness of one of the wall-time timing dependent async tests by forcing a garbage collection at the start of the test.

NeilFraser/CodeCity,google/CodeCity,google/CodeCity,google/CodeCity,NeilFraser/CodeCity,NeilFraser/CodeCity,NeilFraser/CodeCity,google/CodeCity