[turbofan] Properly implement %_ClassOf intrinsic.

src/builtins/builtins.h

Index: src/builtins/builtins.h
diff --git a/src/builtins/builtins.h b/src/builtins/builtins.h
index 53fb4a03571a7888999dc20c194754dbda22b601..a87ded2992fb2f4c9bebcdd8417cde57a90ccbd7 100644
--- a/src/builtins/builtins.h
+++ b/src/builtins/builtins.h
@@ -208,6 +208,7 @@ namespace internal {
   TFS(ToString, BUILTIN, kNoExtraICState, TypeConversion)                      \
   TFS(ToInteger, BUILTIN, kNoExtraICState, TypeConversion)                     \
   TFS(ToLength, BUILTIN, kNoExtraICState, TypeConversion)                      \
+  TFS(ClassOf, BUILTIN, kNoExtraICState, Typeof)                               \
   TFS(Typeof, BUILTIN, kNoExtraICState, Typeof)                                \
   TFS(GetSuperConstructor, BUILTIN, kNoExtraICState, TypeConversion)           \
                                                                                \