Add counters for add/removeEventListener() called with one argument

Source/core/events/EventTarget.idl

 /*
  * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 10 matching lines @@
 // https://dom.spec.whatwg.org/#interface-eventtarget
 
 [
     CheckSecurity=Window,
     WillBeGarbageCollected,
     Exposed=(Window,Worker)
 ] interface EventTarget {
     // FIXME: first 2 args should be required, but throwing TypeError breaks
     // legacy content.  http://crbug.com/353484
     // FIXME: type should not be nullable.
-    // FIXME: capture should have a default value false.
-    [Custom=CallEpilogue] void addEventListener(optional DOMString? type, optional EventListener? listener, optional boolean capture);
-    [Custom=CallEpilogue] void removeEventListener(optional DOMString? type, optional EventListener? listener, optional boolean capture);
+    [Custom=(CallPrologue,CallEpilogue)] void addEventListener(optional DOMString? type = null, optional EventListener? listener = null, optional boolean capture = false);
+    [Custom=(CallPrologue,CallEpilogue)] void removeEventListener(optional DOMString? type = null, optional EventListener? listener = null, optional boolean capture = false);
     [RaisesException] boolean dispatchEvent(Event event);
 };