Do not use js builtins object to determine whether a function is a builtin.

src/objects.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 5880 matching lines @@
   // [compilation_type]: how the the script was compiled. Encoded in the
   // 'flags' field.
   inline CompilationType compilation_type();
   inline void set_compilation_type(CompilationType type);
 
   // [compilation_state]: determines whether the script has already been
   // compiled. Encoded in the 'flags' field.
   inline CompilationState compilation_state();
   inline void set_compilation_state(CompilationState state);
 
+  // [hide_source]: determines whether the script source can be exposed as
+  // function source. Encoded in the 'flags' field.
+  inline bool hide_source();
+  inline void set_hide_source(bool value);
+
   // [origin_options]: optional attributes set by the embedder via ScriptOrigin,
   // and used by the embedder to make decisions about the script. V8 just passes
   // this through. Encoded in the 'flags' field.
   inline v8::ScriptOriginOptions origin_options();
   inline void set_origin_options(ScriptOriginOptions origin_options);
 
   DECLARE_CAST(Script)
 
   // If script source is an external string, check that the underlying
   // resource is accessible. Otherwise, always return true.
@@ skipping 41 matching lines @@
   static const int kSourceUrlOffset = kFlagsOffset + kPointerSize;
   static const int kSourceMappingUrlOffset = kSourceUrlOffset + kPointerSize;
   static const int kSize = kSourceMappingUrlOffset + kPointerSize;
 
  private:
   int GetLineNumberWithArray(int code_pos);
 
   // Bit positions in the flags field.
   static const int kCompilationTypeBit = 0;
   static const int kCompilationStateBit = 1;
-  static const int kOriginOptionsShift = 2;
+  static const int kHideSourceBit = 2;
+  static const int kOriginOptionsShift = 3;
   static const int kOriginOptionsSize = 3;
   static const int kOriginOptionsMask = ((1 << kOriginOptionsSize) - 1)
                                         << kOriginOptionsShift;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(Script);
 };
 
 
 // List of builtin functions we want to identify to improve code
 // generation.
@@ skipping 389 matching lines @@
 
   // Stores opt_count and bailout_reason as bit-fields.
   inline void set_opt_count_and_bailout_reason(int value);
   inline int opt_count_and_bailout_reason() const;
 
   inline void set_disable_optimization_reason(BailoutReason reason);
 
   // Tells whether this function should be subject to debugging.
   inline bool IsSubjectToDebugging();
 
+  // Whether this function is defined in native code or extensions.
+  inline bool IsBuiltin();
+
   // Check whether or not this function is inlineable.
   bool IsInlineable();
 
   // Source size of this function.
   int SourceSize();
 
   // Calculate the instance size.
   int CalculateInstanceSize();
 
   // Calculate the number of in-object properties.
@@ skipping 3821 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_