private Histogram histogram(long timestamp) {
        return new TimeHistogram(application.getServiceType(), timestamp);
    }
most of the features have been delegated to AgentHistogramList upon refactoring
TODO: functionality reduced to creating views - need to be renamed or removed

@author emeroad
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/histogram/AgentTimeHistogram.java