Store builtin index on the builtin code object.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index b750b71a88b75ba5395c4913b7a95c4a5cd04416..192473c86e099f741f509621534e4cbd1806eda6 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -4800,6 +4800,18 @@ void Code::set_profiler_ticks(int ticks) {
 }
 
 
+int Code::builtin_index() {
+  ASSERT_EQ(BUILTIN, kind());
+  return READ_INT32_FIELD(this, kKindSpecificFlags1Offset);
+}
+
+
+void Code::set_builtin_index(int index) {
+  ASSERT_EQ(BUILTIN, kind());
+  WRITE_INT32_FIELD(this, kKindSpecificFlags1Offset, index);
+}
+
+
 unsigned Code::stack_slots() {
   ASSERT(is_crankshafted());
   return StackSlotsField::decode(