Avoid sharing AccessorPairs during Genesis.

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 1201 matching lines @@
     return &global_contexts_list_;
   }
 
 #ifdef DEBUG
   void Print();
   void PrintHandles();
 
   // Verify the heap is in its normal state before or after a GC.
   void Verify();
 
+  // Verify that AccessorPairs are not shared, i.e. make sure that they have
+  // exactly one pointer to them.
+  void VerifyNoAccessorPairSharing();
+
   void OldPointerSpaceCheckStoreBuffer();
   void MapSpaceCheckStoreBuffer();
   void LargeObjectSpaceCheckStoreBuffer();
 
   // Report heap statistics.
   void ReportHeapStatistics(const char* title);
   void ReportCodeStatistics(const char* title);
 
   // Fill in bogus values in from space
   void ZapFromSpace();
@@ skipping 1414 matching lines @@
   AssertNoAllocation no_alloc;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG || LIVE_OBJECT_LIST
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_