Filter old to new references when moving parts of an object.

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 787 matching lines @@
   // Allocates a fixed array initialized with undefined values
   MUST_USE_RESULT MaybeObject* AllocateFixedArray(int length);
 
   // Allocates an uninitialized fixed array. It must be filled by the caller.
   //
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
   // Please note this does not perform a garbage collection.
   MUST_USE_RESULT MaybeObject* AllocateUninitializedFixedArray(int length);
 
+  // Move len elements within a given array from src_index index to dst_index
+  // index.
+  void MoveElements(FixedArray* array, int dst_index, int src_index, int len);
+
   // Make a copy of src and return it. Returns
   // Failure::RetryAfterGC(requested_bytes, space) if the allocation failed.
   MUST_USE_RESULT inline MaybeObject* CopyFixedArray(FixedArray* src);
 
   // Make a copy of src, set the map, and return the copy. Returns
   // Failure::RetryAfterGC(requested_bytes, space) if the allocation failed.
   MUST_USE_RESULT MaybeObject* CopyFixedArrayWithMap(FixedArray* src, Map* map);
 
   // Make a copy of src and return it. Returns
   // Failure::RetryAfterGC(requested_bytes, space) if the allocation failed.
@@ skipping 2023 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_