std::string HostToCustomHistogramSuffix(const std::string& host) {
  if (host == "mail.google.com")
    return ".gmail";
  if (host == "docs.google.com" || host == "drive.google.com")
    return ".docs";
  if (host == "plus.google.com")
    return ".plus";
  return std::string();
}

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.