@Override
  public void onFailure(Call call, IOException ioe) {
    metrics.endNetwork();
    if (callback != null) {
      metrics.endRequest(ioe, 0, retryCounter);
      callback.onFailure(ioe);
    }
  }
Preserve a request/response pair through an asynchronous callback.
src/main/java/com/google/maps/internal/OkHttpPendingResult.java