protected SearchChain buildChain(DeployState deployState, TreeConfigProducer<AnyConfigProducer> ancestor, Element producerSpec,
                                     ChainSpecification specWithoutInnerComponents) {
        return new SearchChain(specWithoutInnerComponents);
    }
Builds a Search chain from xml.
@author Tony Vaagenes
config-model/src/main/java/com/yahoo/vespa/model/builder/xml/dom/chains/search/DomSearchChainBuilder.java