[left-trimming] Avoid creating duplicate handles in builtins.cc

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 1344 matching lines @@
   void TracePathToObject(Object* target);
   void TracePathToGlobal();
 
   void Print();
   void PrintHandles();
 
   // Report heap statistics.
   void ReportHeapStatistics(const char* title);
   void ReportCodeStatistics(const char* title);
 #endif
+#ifdef ENABLE_SLOW_DCHECKS
+  int CountHandlesForObject(Object* object);
+#endif
 
  private:
   class PretenuringScope;
   class UnmapFreeMemoryTask;
 
   // External strings table is a place where all external strings are
   // registered.  We need to keep track of such strings to properly
   // finalize them.
   class ExternalStringTable {
    public:
@@ skipping 1247 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_