Flatten the Arrays returned and consumed by the v8::Map API

src/collection.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.
 
 var $getHash;
 var $getExistingHash;
 var $mapFromArray;
 var $setFromArray;
 
 (function(global, utils) {
@@ skipping 467 matching lines @@
   "forEach", MapForEach
 ]);
 
 // Expose to the global scope.
 $getHash = GetHash;
 $getExistingHash = GetExistingHash;
 
 $mapFromArray = function(array) {
   var map = new GlobalMap;
   var length = array.length;
-  for (var i = 0; i < length; ++i) {
-    var entry = array[i];
-    %_CallFunction(map, entry[0], entry[1], MapSet);
+  for (var i = 0; i < length; i += 2) {
+    var key = array[i];
+    var value = array[i + 1];
+    %_CallFunction(map, key, value, MapSet);
   }
   return map;
 };
 
 $setFromArray = function(array) {
   var set = new GlobalSet;
   var length = array.length;
   for (var i = 0; i < length; ++i) {
     %_CallFunction(set, array[i], SetAdd);
   }
   return set;
 };
 
 })