[builtins] Fix ToString in Array.prototype.join.

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 191 matching lines @@
     return %StringBuilderJoin(elements, length, separator);
   } finally {
     // Make sure to remove the last element of the visited array no
     // matter what happens.
     if (is_array) visited_arrays.length = visited_arrays.length - 1;
   }
 }
 
 
 function ConvertToString(x) {
-  // Assumes x is a non-string.
-  if (IS_NUMBER(x)) return %_NumberToString(x);
-  if (IS_BOOLEAN(x)) return x ? 'true' : 'false';
-  return (IS_NULL_OR_UNDEFINED(x)) ? '' : ToString($defaultString(x));
+  if (IS_NULL_OR_UNDEFINED(x)) {
+    return '';
+  } else {
+    return TO_STRING(x);
+  }
 }
 
 
 function ConvertToLocaleString(e) {
   if (IS_NULL_OR_UNDEFINED(e)) {
     return '';
   } else {
     // According to ES5, section 15.4.4.3, the toLocaleString conversion
     // must throw a TypeError if ToObject(e).toLocaleString isn't
     // callable.
     var e_obj = TO_OBJECT(e);
-    return ToString(e_obj.toLocaleString());
+    return TO_STRING(e_obj.toLocaleString());
   }
 }
 
 
 // This function implements the optimized splice implementation that can use
 // special array operations to handle sparse arrays in a sensible fashion.
 function SparseSlice(array, start_i, del_count, len, deleted_elements) {
   // Move deleted elements to a new array (the return value from splice).
   var indices = %GetArrayKeys(array, start_i + del_count);
   if (IS_NUMBER(indices)) {
@@ skipping 1419 matching lines @@
 %InstallToContext([
   "array_pop", ArrayPop,
   "array_push", ArrayPush,
   "array_shift", ArrayShift,
   "array_splice", ArraySplice,
   "array_slice", ArraySlice,
   "array_unshift", ArrayUnshift,
 ]);
 
 });