public void updateAggregatedStats(AggregatedClusterStats newAggregatedStats,
                                      double minMergeCompletionRatio) {
        syncAggregatedStats();
        setAggregatedStats(newAggregatedStats, minMergeCompletionRatio);
    }
Class tracking whether we have changes in current and previous aggregated cluster stats.

The cluster stats are considered changed if the current and previous stats differs in whether
they may have buckets pending in the 'global' bucket space. This signals that the ClusterStateBundle should be recomputed.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/ClusterStatsChangeTracker.java