8302047: G1: Remove unused G1RegionToSpaceMapper::_region_granularity

Reviewed-by: tschatzl

src/hotspot/share/gc/g1/g1RegionToSpaceMapper.cpp

@@ -43,7 +43,6 @@ G1RegionToSpaceMapper::G1RegionToSpaceMapper(ReservedSpace rs,
                                              MEMFLAGS type) :
   _listener(NULL),
   _storage(rs, used_size, page_size),
-  _region_granularity(region_granularity),
   _region_commit_map(rs.size() * commit_factor / region_granularity, mtGC),
   _memory_type(type) {
   guarantee(is_power_of_2(page_size), "must be");

src/hotspot/share/gc/g1/g1RegionToSpaceMapper.hpp

@@ -49,7 +49,6 @@ class G1RegionToSpaceMapper : public CHeapObj<mtGC> {
   // Backing storage.
   G1PageBasedVirtualSpace _storage;
 
-  size_t _region_granularity;
   // Mapping management
   CHeapBitMap _region_commit_map;