[runtime] Replace %to_string_fun with %_ToString.

test/mjsunit/messages.js

 // 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.
 
 // Flags: --stack-size=100 --harmony --harmony-reflect --harmony-regexps
 // Flags: --harmony-simd --strong-mode
 
 function test(f, expected, type) {
   try {
     f();
@@ skipping 58 matching lines @@
 
 // kConstAssign
 test(function() {
   "use strict";
   const a = 1;
   a = 2;
 }, "Assignment to constant variable.", TypeError);
 
 // kCannotConvertToPrimitive
 test(function() {
-  [].join(Object(Symbol(1)));
+  var o = { toString: function() { return this } };
+  [].join(o);
 }, "Cannot convert object to primitive value", TypeError);
 
 // kCircularStructure
 test(function() {
   var o = {};
   o.o = o;
   JSON.stringify(o);
 }, "Converting circular structure to JSON", TypeError);
 
 // kConstructorNotFunction
@@ skipping 372 matching lines @@
   Number(1).toString(100);
 }, "toString() radix argument must be between 2 and 36", RangeError);
 
 
 // === URIError ===
 
 // kURIMalformed
 test(function() {
   decodeURI("%%");
 }, "URI malformed", URIError);