@Nullable
  private Map<String, String> getExtraMap(FetchState fetchState, int byteSize) {
    if (!fetchState.getListener().requiresExtraMap(fetchState.getContext(), PRODUCER_NAME)) {
      return null;
    }
    return mNetworkFetcher.getExtraMap(fetchState, byteSize);
  }
Time between two consecutive partial results are propagated upstream

<p>TODO 5399646: make this configurable
imagepipeline/src/main/java/com/facebook/imagepipeline/producers/NetworkFetchProducer.java