[d8 Workers] Throw when calling Worker constructor without new

BUG=4399
R=jarin@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/1260813008

Cr-Commit-Position: refs/heads/master@{#30016}

src/d8.cc

@@ -699,6 +699,11 @@ void Shell::WorkerNew(const v8::FunctionCallbackInfo<v8::Value>& args) {
     return;
   }
 
+  if (!args.IsConstructCall()) {
+    Throw(args.GetIsolate(), "Worker must be constructed with new");
+    return;
+  }
+
   {
     base::LockGuard<base::Mutex> lock_guard(workers_mutex_.Pointer());
     // Initialize the internal field to NULL; if we return early without

test/mjsunit/regress-4399.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.
+
+
+if (this.Worker) {
+  assertThrows(function() { Worker.prototype.constructor("55"); });
+}