[runtime] Replace %to_string_fun with %_ToString.

src/array.js

 // Copyright 2012 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.
 
 (function(global, utils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
@@ skipping 393 matching lines @@
 function ArrayToLocaleString() {
   var array = TO_OBJECT(this);
   var arrayLen = array.length;
   return InnerArrayToLocaleString(array, arrayLen);
 }
 
 
 function InnerArrayJoin(separator, array, length) {
   if (IS_UNDEFINED(separator)) {
     separator = ',';
-  } else if (!IS_STRING(separator)) {
-    separator = $nonStringToString(separator);
+  } else {
+    separator = TO_STRING(separator);
   }
 
   var result = %_FastOneByteArrayJoin(array, separator);
   if (!IS_UNDEFINED(result)) return result;
 
   // Fast case for one-element arrays.
   if (length === 1) {
     var e = array[0];
-    if (IS_STRING(e)) return e;
     if (IS_NULL_OR_UNDEFINED(e)) return '';
-    return $nonStringToString(e);
+    return TO_STRING(e);
   }
 
   return Join(array, length, separator, ConvertToString);
 }
 
 
 function ArrayJoin(separator) {
   CHECK_OBJECT_COERCIBLE(this, "Array.prototype.join");
 
   var array = TO_OBJECT(this);
@@ skipping 1221 matching lines @@
 %InstallToContext([
   "array_pop", ArrayPop,
   "array_push", ArrayPush,
   "array_shift", ArrayShift,
   "array_splice", ArraySplice,
   "array_slice", ArraySlice,
   "array_unshift", ArrayUnshift,
 ]);
 
 });