Revert of [d8] bounds-check before getting Shell::Worker internal field

test/mjsunit/regress/regress-4271.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.
-
-// Throw rather than overflow internal field index
-
-assertThrows(function() {
-  Worker.prototype.terminate();
-});
-
-assertThrows(function() {
-  Worker.prototype.getMessage();
-});
-
-assertThrows(function() {
-  Worker.prototype.postMessage({});
-});
-
-// Don't throw for real worker
-
-var worker = new Worker('');
-worker.getMessage();
-worker.postMessage({});
-worker.terminate();