Fix bug 73940.

src/array.js

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1000 matching lines @@
     index = TO_INTEGER(index);
     // 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(this, length, true)) {
+  if (UseSparseVariant(this, length, IS_ARRAY(this))) {
     var intervals = %GetArrayKeys(this, length);
     if (intervals.length == 2 && intervals[0] < 0) {
       // A single interval.
       var intervalMin = -(intervals[0] + 1);
       var intervalMax = intervalMin + intervals[1];
-      min = MAX(min, intervalMin);
+      if (min < intervalMin) min = intervalMin;
       max = intervalMax;  // Capped by length already.
       // Fall through to loop below.
     } else {
       if (intervals.length == 0) return -1;
       // Get all the keys in sorted order.
       var sortedKeys = GetSortedArrayKeys(this, intervals);
       var n = sortedKeys.length;
       var i = 0;
       while (i < n && sortedKeys[i] < index) i++;
       while (i < n) {
@@ skipping 29 matching lines @@
   } else {
     index = TO_INTEGER(index);
     // 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(this, length, true)) {
+  if (UseSparseVariant(this, length, IS_ARRAY(this))) {
     var intervals = %GetArrayKeys(this, index + 1);
     if (intervals.length == 2 && intervals[0] < 0) {
       // A single interval.
       var intervalMin = -(intervals[0] + 1);
       var intervalMax = intervalMin + intervals[1];
-      min = MAX(min, intervalMin);
+      if (min < intervalMin) min = intervalMin;
       max = intervalMax;  // Capped by index already.
       // Fall through to loop below.
     } else {
       if (intervals.length == 0) return -1;
       // Get all the keys in sorted order.
       var sortedKeys = GetSortedArrayKeys(this, intervals);
       var i = sortedKeys.length - 1;
       while (i >= 0) {
         var key = sortedKeys[i];
         if (!IS_UNDEFINED(key) && this[key] === element) return key;
@@ skipping 129 matching lines @@
     "lastIndexOf", getFunction("lastIndexOf", ArrayLastIndexOf, 1),
     "reduce", getFunction("reduce", ArrayReduce, 1),
     "reduceRight", getFunction("reduceRight", ArrayReduceRight, 1)
   ));
 
   %FinishArrayPrototypeSetup($Array.prototype);
 }
 
 
 SetupArray();