Revert of IDL: Support optional argument default value syntax

Source/core/dom/Text.idl

 /*
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * 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.
  */
 [
-    Constructor(optional DOMString data = null),
+    Constructor([Default=NullString] optional DOMString data),
     ConstructorCallWith=Document,
     Custom=Wrap,
 ] interface Text : CharacterData {
 
     // DOM Level 1
     [RaisesException] Text splitText(unsigned long offset);
 
     // Introduced in DOM Level 3:
     readonly attribute DOMString       wholeText;
     [MeasureAs=TextReplaceWholeText] Text replaceWholeText(DOMString content); // Removed from DOM4.
 
     // Shadow DOM API
     NodeList getDestinationInsertionPoints();
 };