PushLayersStep.java

class PushLayersStep
    implements AsyncStep<ImmutableList<AsyncStep<PushBlobStep>>>,
        Callable<ImmutableList<AsyncStep<PushBlobStep>>> {
  /*(...)*/
    private PushBlobStep makePushBlobStep(AsyncStep<? extends CachedLayer> cachedLayerStep)
      throws ExecutionException {
    CachedLayer cachedLayer = NonBlockingSteps.get(cachedLayerStep);
    return new PushBlobStep(
        listeningExecutorService,
        buildConfiguration,
        authenticatePushStep,
        cachedLayer.getBlobDescriptor(),
        cachedLayer.getBlob());
  }
}