[builtins] Remove bunch of uses of %_Arguments and %_ArgumentsLength.

src/js/spread.js

 // Copyright 2015 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';
 
 // -------------------------------------------------------------------
 // Imports
 var InternalArray = utils.InternalArray;
 var MakeTypeError;
 
 utils.Import(function(from) {
   MakeTypeError = from.MakeTypeError;
 });
 
 // -------------------------------------------------------------------
 
 function SpreadArguments() {
-  var count = %_ArgumentsLength();
+  var count = arguments.length;
   var args = new InternalArray();
 
   for (var i = 0; i < count; ++i) {
-    var array = %_Arguments(i);
+    var array = arguments[i];
     var length = array.length;
     for (var j = 0; j < length; ++j) {
       args.push(array[j]);
     }
   }
 
   return args;
 }
 
 
@@ skipping 11 matching lines @@
 
 // ----------------------------------------------------------------------------
 // Exports
 
 %InstallToContext([
   "spread_arguments", SpreadArguments,
   "spread_iterable", SpreadIterable,
 ]);
 
 })