[turbofan] Assign proper type to Object.prototype.toString().

src/objects.h

 // Copyright 2015 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 <memory>
 
@@ skipping 6978 matching lines @@
   V(Date.prototype, getMilliseconds, DateGetMilliseconds)   \
   V(Date.prototype, getMinutes, DateGetMinutes)             \
   V(Date.prototype, getMonth, DateGetMonth)                 \
   V(Date.prototype, getSeconds, DateGetSeconds)             \
   V(Date.prototype, getTime, DateGetTime)                   \
   V(Function.prototype, apply, FunctionApply)               \
   V(Function.prototype, call, FunctionCall)                 \
   V(Object, assign, ObjectAssign)                           \
   V(Object, create, ObjectCreate)                           \
   V(Object.prototype, hasOwnProperty, ObjectHasOwnProperty) \
+  V(Object.prototype, toString, ObjectToString)             \
   V(RegExp.prototype, compile, RegExpCompile)               \
   V(RegExp.prototype, exec, RegExpExec)                     \
   V(RegExp.prototype, test, RegExpTest)                     \
   V(RegExp.prototype, toString, RegExpToString)             \
   V(String.prototype, charCodeAt, StringCharCodeAt)         \
   V(String.prototype, charAt, StringCharAt)                 \
   V(String.prototype, codePointAt, StringCodePointAt)       \
   V(String.prototype, concat, StringConcat)                 \
   V(String.prototype, endsWith, StringEndsWith)             \
   V(String.prototype, includes, StringIncludes)             \
@@ skipping 4712 matching lines @@
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #include "src/objects/object-macros-undef.h"
 
 #endif  // V8_OBJECTS_H_