Implement onunhandledrejection / onrejectionhandled events

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 17 matching lines @@
 
 [
     Exposed=Worker,
 ] interface WorkerGlobalScope : EventTarget {
     readonly attribute WorkerGlobalScope self;
     readonly attribute WorkerLocation location;
 
     void close();
     // TODO(philipj): onerror should be an OnErrorEventHandler.
     attribute EventHandler onerror;
+    [RuntimeEnabled=PromiseRejectionEvent] attribute EventHandler onrejectionhandled;
+    [RuntimeEnabled=PromiseRejectionEvent] attribute EventHandler onunhandledrejection;
     // attribute EventHandler onlanguagechange;
     // attribute EventHandler onoffline;
     // attribute EventHandler ononline;
 
     // https://html.spec.whatwg.org/#apis-available-to-workers
     [RaisesException] void importScripts(DOMString... urls);
     readonly attribute WorkerNavigator navigator;
 
     // Console API (non-standard but widely implemented in some form)
     // https://developer.chrome.com/devtools/docs/console-api
     [Replaceable] readonly attribute WorkerConsole console;
 };
 
 WorkerGlobalScope implements WindowBase64;
 WorkerGlobalScope implements WindowTimers;