Avoid write barrier when writing an external pointer to an internal field.

src/objects.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 1665 matching lines @@
   MUST_USE_RESULT MaybeObject* SetElementsLength(Object* length);
 
   // Get the header size for a JSObject.  Used to compute the index of
   // internal fields as well as the number of internal fields.
   inline int GetHeaderSize();
 
   inline int GetInternalFieldCount();
   inline int GetInternalFieldOffset(int index);
   inline Object* GetInternalField(int index);
   inline void SetInternalField(int index, Object* value);
+  inline void SetInternalField(int index, Smi* value);
 
   // The following lookup functions skip interceptors.
   void LocalLookupRealNamedProperty(String* name, LookupResult* result);
   void LookupRealNamedProperty(String* name, LookupResult* result);
   void LookupRealNamedPropertyInPrototypes(String* name, LookupResult* result);
   void LookupCallbackSetterInPrototypes(String* name, LookupResult* result);
   MUST_USE_RESULT MaybeObject* SetElementWithCallbackSetterInPrototypes(
       uint32_t index, Object* value, bool* found, StrictModeFlag strict_mode);
   void LookupCallback(String* name, LookupResult* result);
 
@@ skipping 6179 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_