Fix Array.prototype.sort on proxies.

test/mjsunit/array-sort.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 446 matching lines @@
   Number.prototype.length = 2;
   x = new Number(0);
   assertEquals(0, Number(Array.prototype.sort.call(x)));
   assertEquals(4, x[0]);
   assertEquals(5, x[1]);
   assertArrayEquals(["0", "1"], Object.getOwnPropertyNames(x));
   // The following would throw if ToObject weren't called.
   assertEquals(0, Number(Array.prototype.sort.call(0)));
 }
 TestSortToObject();
+
+function TestSortOnProxy() {
+  var p = new Proxy([2,1,3], {});
+  assertEquals([1,2,3], p.sort());
+}
+TestSortOnProxy();