Scheduler/child/TimeSource could be replaced with base/time/DefaultTickClock.

They both are totally same and TimeSource is removed.

BUG=494892
R=skyostil@chromium.org, mithro@mithis.com

Review URL: https://codereview.chromium.org/1163143002

Cr-Commit-Position: refs/heads/master@{#333035}
TaskQueueManager::QueueState TaskQueue::GetQueueState() const {
  DCHECK(main_thread_checker_.CalledOnValidThread());
  if (!work_queue_.empty())
    return TaskQueueManager::QueueState::HAS_WORK;

  {
    base::AutoLock lock(lock_);
    if (incoming_queue_.empty()) {
      return TaskQueueManager::QueueState::EMPTY;
    } else {
      return TaskQueueManager::QueueState::NEEDS_PUMPING;
    }
  }
}

TaskQueueManager::QueueState TaskQueue::GetQueueState() const {
  DCHECK(main_thread_checker_.CalledOnValidThread());
  if (!work_queue_.empty())
    return TaskQueueManager::QueueState::HAS_WORK;

  {
    base::AutoLock lock(lock_);
    if (incoming_queue_.empty()) {
      return TaskQueueManager::QueueState::EMPTY;
    } else {
      return TaskQueueManager::QueueState::NEEDS_PUMPING;
    }
  }
}
