Freeze global prototype chain per WebIDL

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // https://drafts.css-houdini.org/worklets/#workletglobalscope
 
 [
     Exposed=Worklet,
     RuntimeEnabled=Worklet,
+    ImmutablePrototype,
 ] interface WorkletGlobalScope {
     // Console API
     // https://console.spec.whatwg.org/#console-interface
     // [Replaceable] readonly attribute Console console;
     // Console is installed by v8 inspector when context is created
     // and is left commented here just for documentation.
 };