The index argument for HTMLTableRowElement deleteCell() api should not be optional

Source/core/html/HTMLTableRowElement.idl

 /*
  * Copyright (C) 2006, 2007, 2010 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,
  * 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/#the-tr-element
 
 interface HTMLTableRowElement : HTMLElement {
     readonly attribute long rowIndex;
     readonly attribute long sectionRowIndex;
     readonly attribute HTMLCollection cells;
     [RaisesException] HTMLElement insertCell(optional long index = -1);
-    // TODO(philipj): The index argument should not be optional.
-    [RaisesException] void deleteCell([Default=Undefined] optional long index);
+    [RaisesException] void deleteCell(long index);
 
     // obsolete members
     // https://html.spec.whatwg.org/#HTMLTableRowElement-partial
     [Reflect] attribute DOMString align;
     [Reflect=char] attribute DOMString ch;
     [Reflect=charoff] attribute DOMString chOff;
     [Reflect] attribute DOMString vAlign;
 
     [Reflect, TreatNullAs=EmptyString] attribute DOMString bgColor;
 };