[builtins] Add support for JS builtins written in TurboFan.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 558d3fa2645c972922cc201d6235f2ba207e02f8..0a0f9693206dc47749ac68ad74dad00fd52accf2 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5319,8 +5319,9 @@ class Code: public HeapObject {
   // Note: We might be able to squeeze this into the flags above.
   static const int kPrologueOffset = kKindSpecificFlags2Offset + kIntSize;
   static const int kConstantPoolOffset = kPrologueOffset + kIntSize;
-  static const int kHeaderPaddingStart =
+  static const int kBuiltinIndexOffset =
       kConstantPoolOffset + kConstantPoolSize;
+  static const int kHeaderPaddingStart = kBuiltinIndexOffset + kIntSize;
 
   // Add padding to align the instruction start following right after
   // the Code object header.
@@ -5348,7 +5349,7 @@ class Code: public HeapObject {
       : public BitField<ExtraICState, 11, PlatformSmiTagging::kSmiValueSize -
                                               11 + 1> {};  // NOLINT
 
-  // KindSpecificFlags1 layout (STUB and OPTIMIZED_FUNCTION)
+  // KindSpecificFlags1 layout (STUB, BUILTIN and OPTIMIZED_FUNCTION)
   static const int kStackSlotsFirstBit = 0;
   static const int kStackSlotsBitCount = 24;
   static const int kMarkedForDeoptimizationBit =