Change the check for builtin functions to not be based on identity,...

src/objects.h

 // Copyright 2006-2009 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 3157 matching lines @@
   // when the function is invoked, e.g. foo() or new foo(). See
   // [[Call]] and [[Construct]] description in ECMA-262, section
   // 8.6.2, page 27.
   inline Code* code();
   inline void set_code(Code* value);
 
   // Tells whether this function is a context-independent boilerplate
   // function.
   inline bool IsBoilerplate();
 
+  // Tells whether this function is builtin.
+  inline bool IsBuiltin();
+
   // [literals]: Fixed array holding the materialized literals.
   //
   // If the function contains object, regexp or array literals, the
   // literals array prefix contains the object, regexp, and array
   // function to be used when creating these literals.  This is
   // necessary so that we do not dynamically lookup the object, regexp
   // or array functions.  Performing a dynamic lookup, we might end up
   // using the functions from a new context that we should not have
   // access to.
   DECL_ACCESSORS(literals, FixedArray)
@@ skipping 1597 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_