Introduce a new AccessorPair type for handling JavaScript accessors.

src/heap.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
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   // Allocates an empty code cache.
   MUST_USE_RESULT MaybeObject* AllocateCodeCache();
 
   // Allocates a serialized scope info.
   MUST_USE_RESULT MaybeObject* AllocateScopeInfo(int length);
 
   // Allocates an empty PolymorphicCodeCache.
   MUST_USE_RESULT MaybeObject* AllocatePolymorphicCodeCache();
 
+  // Allocates a pre-tenured empty AccessorPair.
+  MUST_USE_RESULT MaybeObject* AllocateAccessorPair();
+
   // Clear the Instanceof cache (used when a prototype changes).
   inline void ClearInstanceofCache();
 
   // Allocates and fully initializes a String.  There are two String
   // encodings: ASCII and two byte. One should choose between the three string
   // allocation functions based on the encoding of the string buffer used to
   // initialized the string.
   //   - ...FromAscii initializes the string from a buffer that is ASCII
   //     encoded (it does not check that the buffer is ASCII encoded) and the
   //     result will be ASCII encoded.
@@ skipping 1982 matching lines @@
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG || LIVE_OBJECT_LIST
 
 } }  // namespace v8::internal
 
 #undef HEAP
 
 #endif  // V8_HEAP_H_