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 28 matching lines @@
     // 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;
+
+    // Unhandled Promise Rejection Events
+    // https://github.com/domenic/unhandled-rejections-browser-spec
+    [RuntimeEnabled=PromiseRejectionEvent] attribute EventHandler onrejectionhandled;
+    [RuntimeEnabled=PromiseRejectionEvent] attribute EventHandler onunhandledrejection;
 };
 
 WorkerGlobalScope implements WindowBase64;
 WorkerGlobalScope implements WindowTimers;