ResourceDispatcherHostImpl::IncrementOutstandingRequestsMemory(
    int count,
    const ResourceRequestInfoImpl& info) {
  DCHECK_EQ(1, abs(count));

  OustandingRequestsStats stats = GetOutstandingRequestsStats(info);

  stats.memory_cost += count * info.memory_cost();
  DCHECK_GE(stats.memory_cost, 0);
  UpdateOutstandingRequestsStats(info, stats);

  return stats;
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.