[elements] revert overzealous optimzation for fast sloppy arguments delete

test/mjsunit/arguments.js

 // Copyright 2011 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 186 matching lines @@
   // Turn arguments into slow.
   assertTrue(%HasSloppyArgumentsElements(a));
   a[10000] = 1;
   assertTrue(%HasSloppyArgumentsElements(a));
   // Make it fast again by adding values.
   for (var i = 0; i < 1000; i++) {
     a[i] = 1.5;
   }
   assertTrue(%HasSloppyArgumentsElements(a));
 })();
+
+(function testDeleteArguments() {
+  function f() { return arguments };
+  var args = f(1, 2);
+  assertEquals(1, args[0]);
+  assertEquals(2, args[1]);
+  assertEquals(2, args.length);
+
+  delete args[0];
+  assertEquals(undefined, args[0]);
+  assertEquals(2, args[1]);
+  assertEquals(2, args.length);
+
+  delete args[1];
+  assertEquals(undefined, args[0]);
+  assertEquals(undefined, args[1]);
+  assertEquals(2, args.length);
+})();
+
+(function testDeleteFastSloppyArguments() {
+  function f(a) { return arguments };
+  var args = f(1, 2);
+  assertEquals(1, args[0]);
+  assertEquals(2, args[1]);
+  assertEquals(2, args.length);
+
+  delete args[0];
+  assertEquals(undefined, args[0]);
+  assertEquals(2, args[1]);
+  assertEquals(2, args.length);
+
+  delete args[1];
+  assertEquals(undefined, args[0]);
+  assertEquals(undefined, args[1]);
+  assertEquals(2, args.length);
+})();
+
+(function testDeleteSlowSloppyArguments() {
+  var key = 10000;
+  function f(a) {
+    arguments[key] = key;
+    return arguments
+  };
+  var args = f(1, 2);
+  assertEquals(1, args[0]);
+  assertEquals(2, args[1]);
+  assertEquals(key, args[key]);
+  assertEquals(2, args.length);
+
+  delete args[0];
+  assertEquals(undefined, args[0]);
+  assertEquals(2, args[1]);
+  assertEquals(key, args[key]);
+  assertEquals(2, args.length);
+
+  delete args[1];
+  assertEquals(undefined, args[0]);
+  assertEquals(undefined, args[1]);
+  assertEquals(key, args[key]);
+  assertEquals(2, args.length);
+
+  delete args[key];
+  assertEquals(undefined, args[0]);
+  assertEquals(undefined, args[1]);
+  assertEquals(undefined, args[key]);
+  assertEquals(2, args.length);
+})();