@Nullable
  protected RequestListener getRequestListener(final DraweeController controller) {
    if (controller instanceof PipelineDraweeController) {
      return ((PipelineDraweeController) controller).getRequestListener();
    }
    return null;
  }
Concrete implementation of ImagePipeline Drawee controller builder.

<p>See {@link AbstractDraweeControllerBuilder} for more details.
drawee-backends/drawee-pipeline/src/main/java/com/facebook/drawee/backends/pipeline/PipelineDraweeControllerBuilder.java