@Override
    protected void onFailureImpl(@Nullable Throwable t) {
      mInputProducer2.produceResults(getConsumer(), mProducerContext);
    }
Producer that coordinates fetching two separate images.

<p>The first producer is kicked off, and once it has returned all its results, the second
producer is kicked off if necessary.
imagepipeline/src/main/java/com/facebook/imagepipeline/producers/BranchOnSeparateImagesProducer.java