Currently, G1RegionMarkStatsCache constructor does not call G1RegionMarkStatsCache::reset(), it depends on user to call it explicitly to make sure it works well and without crash in G1RegionMarkStatsCache::evict(uint idx).

In fact G1RegionMarkStatsCache constructor should call G1RegionMarkStatsCache::reset() to ensure its valid initial state.

( I met this issue when I tried to reuse this class to implement some parallel cache when improve the parallelism of evacuation failure. )