Update the FIXME around event handler attributes on body/frameset

Source/core/html/HTMLFrameSetElement.idl

 /*
  * Copyright (C) 2006, 2007, 2009, 2010 Apple Inc. All rights reserve
  * 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,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 // https://html.spec.whatwg.org/#htmlframesetelement
 
 // FIXME: HTMLFrameSetElement should not have [OverrideBuiltins].
 [
     OverrideBuiltins,
 ] interface HTMLFrameSetElement : HTMLElement {
     [Reflect] attribute DOMString cols;
     [Reflect] attribute DOMString rows;
 
-    // FIXME: The spec requires special behavior for these event
-    // handler attributes but does not include them in the IDL:
-    // https://www.w3.org/Bugs/Public/show_bug.cgi?id=28166
+    // TODO(philipj): These event handler attributes should be inherited from
+    // HTMLElement (which implements GlobalEventHandlers), but have different
+    // behavior. See https://www.w3.org/Bugs/Public/show_bug.cgi?id=28166
     attribute EventHandler onblur;
     attribute EventHandler onerror;
     attribute EventHandler onfocus;
     attribute EventHandler onload;
     attribute EventHandler onresize;
     attribute EventHandler onscroll;
 
     // Non-standard APIs
     [NotEnumerable] getter Window (DOMString name);
     [RuntimeEnabled=OrientationEvent] attribute EventHandler onorientationchange;
 };
 
 HTMLFrameSetElement implements WindowEventHandlers;