Implicit references are missing in heap profiles

src/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1620 matching lines @@
     return &error_object_list_;
   }
 
   // Returns the current sweep generation.
   int sweep_generation() {
     return sweep_generation_;
   }
 
   inline Isolate* isolate();
 
-  inline void CallGlobalGCPrologueCallback() {
-    if (global_gc_prologue_callback_ != NULL) global_gc_prologue_callback_();
-  }
-
-  inline void CallGlobalGCEpilogueCallback() {
-    if (global_gc_epilogue_callback_ != NULL) global_gc_epilogue_callback_();
-  }
+  void CallGCPrologueCallbacks(GCType gc_type);
+  void CallGCEpilogueCallbacks(GCType gc_type);
 
   inline bool OldGenerationAllocationLimitReached();
 
   inline void DoScavengeObject(Map* map, HeapObject** slot, HeapObject* obj) {
     scavenging_visitors_table_.GetVisitor(map)(map, slot, obj);
   }
 
   void QueueMemoryChunkForFree(MemoryChunk* chunk);
   void FreeQueuedChunks();
 
@@ skipping 1239 matching lines @@
   AssertNoAllocation no_alloc;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_