Use [TreatNullAs=EmptyString] for DOMString attributes with [Reflect]

Source/core/html/HTMLImageElement.idl

 /*
  * Copyright (C) 2006, 2009, 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.
  */
 
 // FIXME: NamedConstructor does not support optional without Default. Fortunately using Undefined makes
 // us use 0 which happens to be the default width and height anyway.
 [
     NamedConstructor=Image([Default=Undefined] optional long width, [Default=Undefined] optional long height),
     ConstructorCallWith=Document
 ] interface HTMLImageElement : HTMLElement {
     [Reflect] attribute DOMString align;
     [Reflect] attribute DOMString alt;
-    [Reflect, TreatNullAs=NullString] attribute DOMString border;
+    [Reflect, TreatNullAs=EmptyString] attribute DOMString border;
     readonly attribute boolean complete;
     [Reflect, ReflectOnly="anonymous"|"use-credentials", ReflectEmpty="anonymous", ReflectInvalid="anonymous"] attribute DOMString crossOrigin;
     attribute long height;
     [Reflect] attribute long hspace;
     [Reflect] attribute boolean isMap;
     [Reflect, URL] attribute DOMString longDesc;
     [Reflect, URL] attribute DOMString lowsrc;
     [Reflect] attribute DOMString name;
     readonly attribute long naturalHeight;
     readonly attribute long naturalWidth;
     [Reflect, URL] attribute DOMString src;
     [Reflect] attribute DOMString srcset;
     [Reflect, RuntimeEnabled=PictureSizes] attribute DOMString sizes;
     [RuntimeEnabled=PictureSizes] readonly attribute DOMString currentSrc;
     [Reflect] attribute DOMString useMap;
     [Reflect] attribute long vspace;
     attribute long width;
 
     // Extensions
     [MeasureAs=HTMLImageElementX] readonly attribute long x;
     [MeasureAs=HTMLImageElementY] readonly attribute long y;
 
     [Reflect, RuntimeEnabled=SubresourceIntegrity] attribute DOMString integrity;
 };