--- old/src/hotspot/share/gc/g1/g1CollectedHeap.hpp	2018-09-04 14:50:25.127665165 +0000
+++ new/src/hotspot/share/gc/g1/g1CollectedHeap.hpp	2018-09-04 14:50:24.971663426 +0000
@@ -132,6 +132,7 @@
   friend class VM_CollectForMetadataAllocation;
   friend class VM_G1CollectForAllocation;
   friend class VM_G1CollectFull;
+  friend class VM_G1IdleCompaction;
   friend class VMStructs;
   friend class MutatorAllocRegion;
   friend class G1FullCollector;
@@ -1408,6 +1409,12 @@
   size_t pending_card_num();
 
 private:
+  // Elapsed time since last call to resize_if_necessary_after_full_collection
+  double _last_heap_resize;
+public:
+  double last_heap_resize() { return _last_heap_resize; }
+
+private:
   size_t _max_heap_capacity;
 };