private NodeHistogramFactory createNodeHistogramFactory() {
        WasNodeHistogramDataSource wasNodeHistogramDataSource = new MapResponseNodeHistogramDataSource(mapResponseDao);
        return new DefaultNodeHistogramFactory(wasNodeHistogramDataSource);
    }
@author HyunGil Jeong
@author jaehong.kim
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/service/ResponseTimeHistogramServiceImpl.java