public static @Nullable ImageRequest fromUri(@Nullable String uriString) {
    return (uriString == null || uriString.length() == 0) ? null : fromUri(Uri.parse(uriString));
  }
Custom downsample override for this request. null -> use default pipeline's setting.
imagepipeline/src/main/java/com/facebook/imagepipeline/request/ImageRequest.java