Merge "Deflake WorkerThreadTest" into sc-dev am: 47264c7a

    constexpr int NUM_TASKS = 10000;

    WorkerThread worker(NUM_TASKS);

    std::mutex mut;

    std::condition_variable cv;

    bool finished = false;

    std::vector<int> results;

    for (int i = 0; i < NUM_TASKS; ++i) {

        worker.schedule(Callable::from([&results, i] {

        worker.schedule(Callable::from([&mut, &results, i] {

            // Delay tasks differently to provoke races.

            std::this_thread::sleep_for(std::chrono::nanoseconds(100 - i % 100));

            // Unguarded write to results to provoke races.

            auto lock = std::lock_guard(mut);

            results.push_back(i);

        }));

    }

    std::promise<void> promise;

    auto future = promise.get_future();

    // Schedule a special task to signal when all of the tasks are finished.

    worker.schedule(

            Callable::from([promise = std::move(promise)]() mutable { promise.set_value(); }));

    future.wait();

    worker.schedule(Callable::from([&mut, &cv, &finished] {

        auto lock = std::lock_guard(mut);

        finished = true;

        cv.notify_one();

    }));

    auto lock = std::unique_lock(mut);

    cv.wait(lock, [&finished] { return finished; });

    ASSERT_EQ(results.size(), NUM_TASKS);

    EXPECT_TRUE(std::is_sorted(results.begin(), results.end()));

}