8014405: G1: PerRegionTable::fl_mem_size() calculates size of the free list using wrong element sizes

Instead of using a simple sizeof(), ask the PerRegionTable class about its size when iterating over the free list.

Reviewed-by: jwilhelm, brutisso

hotspot/src/share/vm/gc_implementation/g1/heapRegionRemSet.hpp

@@ -338,6 +338,7 @@ public:
 
   // Run unit tests.
 #ifndef PRODUCT
+  static void test_prt();
   static void test();
 #endif
 };