Fix array concat to follow the specification in the presence of element getters.

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 400 matching lines @@
   var m = %_ArgumentsLength();
   for (var i = 0; i < m; i++) {
     this[i+n] = %_Arguments(i);
   }
   this.length = n + m;
   return this.length;
 }
 
 
 function ArrayConcat(arg1) {  // length == 1
-  // TODO: can we just use arguments?
   var arg_count = %_ArgumentsLength();
   var arrays = new $Array(1 + arg_count);
   arrays[0] = this;
   for (var i = 0; i < arg_count; i++) {
     arrays[i + 1] = %_Arguments(i);
   }
 
   return %ArrayConcat(arrays);
 }
 
@@ skipping 791 matching lines @@
     "lastIndexOf", getFunction("lastIndexOf", ArrayLastIndexOf, 1),
     "reduce", getFunction("reduce", ArrayReduce, 1),
     "reduceRight", getFunction("reduceRight", ArrayReduceRight, 1)
   ));
 
   %FinishArrayPrototypeSetup($Array.prototype);
 }
 
 
 SetupArray();