[heap] Remove Heap::TracePath* functions.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 6b65f9d0ac0a7b224798c700772f44374bca2382..dc86608b79326954d8119bbe039d10e5b4a44856 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -1489,10 +1489,6 @@ class Heap {
 #ifdef DEBUG
   void set_allocation_timeout(int timeout) { allocation_timeout_ = timeout; }
 
-  void TracePathToObjectFrom(Object* target, Object* root);
-  void TracePathToObject(Object* target);
-  void TracePathToGlobal();
-
   void Print();
   void PrintHandles();