Refactor UnionOfKeys into ElementsAccessor

src/elements.h

 // Copyright 2011 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 29 matching lines @@
   ElementsAccessor() { }
   virtual ~ElementsAccessor() { }
   virtual MaybeObject* GetWithReceiver(JSObject* obj,
                                        Object* receiver,
                                        uint32_t index) = 0;
 
   virtual MaybeObject* Delete(JSObject* obj,
                               uint32_t index,
                               JSReceiver::DeleteMode mode) = 0;
 
+  virtual MaybeObject* AddJSArrayKeysToFixedArray(JSArray* other,
+                                                  FixedArray* keys) = 0;
+
   // Returns a shared ElementsAccessor for the specified ElementsKind.
   static ElementsAccessor* ForKind(JSObject::ElementsKind elements_kind) {
     ASSERT(elements_kind < JSObject::kElementsKindCount);
     return elements_accessors_[elements_kind];
   }
 
   static void InitializeOncePerProcess();
 
  private:
   static ElementsAccessor** elements_accessors_;
 
   DISALLOW_COPY_AND_ASSIGN(ElementsAccessor);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_ELEMENTS_H_