diff -r ca1f2d4d4ec8 -r f945444fabc3 src/hotspot/share/gc/shared/collectedHeap.hpp
--- a/src/hotspot/share/gc/shared/collectedHeap.hpp	Mon May 07 14:57:23 2018 +0200
+++ b/src/hotspot/share/gc/shared/collectedHeap.hpp	Mon May 07 14:57:25 2018 +0200
@@ -597,6 +597,9 @@
   virtual oop pin_object(JavaThread* thread, oop obj);
   virtual void unpin_object(JavaThread* thread, oop obj);
 
+  // Deduplicate the string, iff the GC supports string deduplication.
+  virtual void deduplicate_string(oop str);
+
   virtual bool is_oop(oop object) const;
 
   // Non product verification and debugging.