Ensure Array.prototype.indexOf returns +0 rather than -0

src/js/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, extrasUtils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
@@ skipping 1329 matching lines @@
 
 // For .indexOf, we don't need to pass in the number of arguments
 // at the callsite since ToInteger(undefined) == 0; however, for
 // .lastIndexOf, we need to pass it, since the behavior for passing
 // undefined is 0 but for not including the argument is length-1.
 function InnerArrayIndexOf(array, element, index, length) {
   if (length == 0) return -1;
   if (IS_UNDEFINED(index)) {
     index = 0;
   } else {
-    index = TO_INTEGER(index);
+    index = TO_INTEGER(index) + 0;  // Add 0 to convert -0 to 0
     // If index is negative, index from the end of the array.
     if (index < 0) {
       index = length + index;
       // If index is still negative, search the entire array.
       if (index < 0) index = 0;
     }
   }
   var min = index;
   var max = length;
   if (UseSparseVariant(array, length, IS_ARRAY(array), max - min)) {
@@ skipping 41 matching lines @@
   var length = TO_LENGTH(this.length);
   return InnerArrayIndexOf(this, element, index, length);
 }
 
 
 function InnerArrayLastIndexOf(array, element, index, length, argumentsLength) {
   if (length == 0) return -1;
   if (argumentsLength < 2) {
     index = length - 1;
   } else {
-    index = TO_INTEGER(index);
+    index = TO_INTEGER(index) + 0;  // Add 0 to convert -0 to 0
     // If index is negative, index from end of the array.
     if (index < 0) index += length;
     // If index is still negative, do not search the array.
     if (index < 0) return -1;
     else if (index >= length) index = length - 1;
   }
   var min = 0;
   var max = index;
   if (UseSparseVariant(array, length, IS_ARRAY(array), index)) {
     %NormalizeElements(array);
@@ skipping 528 matching lines @@
 %InstallToContext([
   "array_pop", ArrayPop,
   "array_push", ArrayPush,
   "array_shift", ArrayShift,
   "array_splice", ArraySplice,
   "array_slice", ArraySlice,
   "array_unshift", ArrayUnshift,
 ]);
 
 });