--- old/src/hotspot/share/gc/g1/g1ParScanThreadState.hpp	2018-11-27 18:26:19.392046485 +0100
+++ new/src/hotspot/share/gc/g1/g1ParScanThreadState.hpp	2018-11-27 18:26:18.968044382 +0100
@@ -239,6 +239,7 @@
   ~G1ParScanThreadStateSet();
 
   void flush();
+  void free_unused_optional_region(HeapRegion* hr);
 
   G1ParScanThreadState* state_for_worker(uint worker_id);