After JDK-8038930 the calculation of the static memory used by the code root chunk manager is wrong: instead of

 86 size_t G1CodeRootChunkManager::static_mem_size() {
 87 return sizeof(this);
 88 }

Also in other places the code uses sizeof(this) instead of sizeof(class name), e.g.

$ grep -r "sizeof(this)" src/share/vm/gc_implementation/g1/
src/share/vm/gc_implementation/g1/sparsePRT.cpp: return sizeof(this) +
src/share/vm/gc_implementation/g1/sparsePRT.cpp: return sizeof(this) +_next->mem_size();
src/share/vm/gc_implementation/g1/g1CodeCacheRemSet.cpp: return sizeof(this);
src/share/vm/gc_implementation/g1/g1CodeCacheRemSet.cpp: return sizeof(this) + _list.count() * _list.size();
src/share/vm/gc_implementation/g1/heapRegionRemSet.hpp: + (sizeof(this) - sizeof(OtherRegionsTable))
src/share/vm/gc_implementation/g1/heapRegionRemSet.cpp: return sizeof(this) + _bm.size_in_words() * HeapWordSize;

All these terms are wrong, should use sizeof(*this) or sizeof(class name).

Fix this.