Faster moving FixedArray elements around.

src/heap.h

 // Copyright 2006-2008 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 753 matching lines @@
   // Makes a new symbol object
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
   // Please note this function does not perform a garbage collection.
   static Object* CreateSymbol(const char* str, int length, int hash);
   static Object* CreateSymbol(String* str);
 
   // Write barrier support for address[offset] = o.
   static inline void RecordWrite(Address address, int offset);
 
+  // Write barrier support for address[start : start + len[ = o.
+  static inline void RecordWrites(Address address, int start, int len);
+
   // Given an address occupied by a live code object, return that object.
   static Object* FindCodeObject(Address a);
 
   // Invoke Shrink on shrinkable spaces.
   static void Shrink();
 
   enum HeapState { NOT_IN_GC, SCAVENGE, MARK_COMPACT };
   static inline HeapState gc_state() { return gc_state_; }
 
 #ifdef DEBUG
@@ skipping 947 matching lines @@
 
   // To speed up scavenge collections new space string are kept
   // separate from old space strings.
   static List<Object*> new_space_strings_;
   static List<Object*> old_space_strings_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_