// Scale down.
		scaled, _, err := dc.scaleReplicaSetAndRecordEvent(ctx, newRS, *(deployment.Spec.Replicas), deployment)
		return scaled, err
	}
	newReplicasCount, err := deploymentutil.NewRSNewReplicas(deployment, allRSs, newRS)
	if err != nil {
		return false, err
	}
	scaled, _, err := dc.scaleReplicaSetAndRecordEvent(ctx, newRS, newReplicasCount, deployment)
	return scaled, err
}

	scaled := false
	for i := range oldRSs {
		rs := oldRSs[i]
		// Scaling not required.
		if *(rs.Spec.Replicas) == 0 {
			continue
		}
		scaledRS, updatedRS, err := dc.scaleReplicaSetAndRecordEvent(ctx, rs, 0, deployment)
		if err != nil {
			return false, err
		}
		if scaledRS {
			oldRSs[i] = updatedRS
			scaled = true
		}
	}
	return scaled, nil
}

	if activeOrLatest := deploymentutil.FindActiveOrLatest(newRS, oldRSs); activeOrLatest != nil {
		if *(activeOrLatest.Spec.Replicas) == *(deployment.Spec.Replicas) {
			return nil
		}
		_, _, err := dc.scaleReplicaSetAndRecordEvent(ctx, activeOrLatest, *(deployment.Spec.Replicas), deployment)
		return err
	}

	// If the new replica set is saturated, old replica sets should be fully scaled down.