Revert of Revert of Protect the emptiness of Array prototype elements with a PropertyCell.

test/mjsunit/elide-double-hole-check-12.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.
+
+// Flags: --allow-natives-syntax
+
+function f1(a, i) {
+  return a[i] + 0.5;
+}
+
+var other_realm = Realm.create();
+var arr = [,0.0,2.5];
+assertEquals(0.5, f1(arr, 1));
+assertEquals(0.5, f1(arr, 1));
+%OptimizeFunctionOnNextCall(f1);
+assertEquals(0.5, f1(arr, 1));
+
+Realm.shared = arr.__proto__;
+
+// The call syntax is useful to make sure the native context is that of the
+// other realm.
+Realm.eval(other_realm, "Array.prototype.push.call(Realm.shared, 1);");
+assertEquals(1.5, f1(arr, 0));