Freeze global prototype chain per WebIDL

third_party/WebKit/Source/core/workers/WorkerGlobalScope.idl

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 12 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */
 
 // https://html.spec.whatwg.org/#the-workerglobalscope-common-interface
 
 [
     ActiveScriptWrappable,
     DependentLifetime,
     Exposed=Worker,
+    ImmutablePrototype,
 ] interface WorkerGlobalScope : EventTarget {
     readonly attribute WorkerGlobalScope self;
     readonly attribute WorkerLocation location;
 
     // TODO(foolip): onerror should be an OnErrorEventHandler.
     attribute EventHandler onerror;
     // attribute EventHandler onlanguagechange;
     // attribute EventHandler onoffline;
     // attribute EventHandler ononline;
 
@@ skipping 16 matching lines @@
     attribute EventHandler onrejectionhandled;
     attribute EventHandler onunhandledrejection;
 
     // Secure Contexts
     // https://w3c.github.io/webappsec-secure-contexts/#dom-windoworworkerglobalscope-issecurecontext
     [ImplementedAs=isSecureContextForBindings] readonly attribute boolean isSecureContext;
 };
 
 WorkerGlobalScope implements WindowBase64;
 WorkerGlobalScope implements WindowTimers;