void ResourceDispatcherHostImpl::CancelRequest(int child_id,
                                               int request_id) {
  ResourceLoader* loader = GetLoader(child_id, request_id);
  if (!loader) {
    DVLOG(1) << "Canceling a request that wasn't found";
    return;
  }

  RemovePendingRequest(child_id, request_id);
}

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.