[builtins] Object.prototype.toString() as TurboFan stub.

src/builtins/builtins.h

Index: src/builtins/builtins.h
diff --git a/src/builtins/builtins.h b/src/builtins/builtins.h
index 11bc9778bf001cd5d8bbf2f5fb0d42bb9fae4f7f..6ee9d53dac8d77320405da7307f64c1a9d53c55c 100644
--- a/src/builtins/builtins.h
+++ b/src/builtins/builtins.h
@@ -331,8 +331,8 @@ namespace internal {
   CPP(ObjectLookupGetter)                                                   \
   CPP(ObjectLookupSetter)                                                   \
   CPP(ObjectPreventExtensions)                                              \
+  TFJ(ObjectProtoToString, 1)                                               \
   CPP(ObjectPrototypePropertyIsEnumerable)                                  \
-  CPP(ObjectProtoToString)                                                  \
   CPP(ObjectSeal)                                                           \
   CPP(ObjectValues)                                                         \
   /* Proxy */                                                               \
@@ -746,6 +746,9 @@ class Builtins {
   // ES6 section 19.1.3.2 Object.prototype.hasOwnProperty
   static void Generate_ObjectHasOwnProperty(CodeStubAssembler* assembler);
 
+  // ES6 section 19.1.3.6 Object.prototype.toString ()
+  static void Generate_ObjectProtoToString(CodeStubAssembler* assembler);
+
   // ES6 section 22.1.2.2 Array.isArray
   static void Generate_ArrayIsArray(CodeStubAssembler* assembler);