Make 'crossOrigin' IDL attributes nullable

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,
@@ skipping 10 matching lines @@
 // 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=EmptyString] attribute DOMString border;
     readonly attribute boolean complete;
-    [Reflect, ReflectOnly=("anonymous","use-credentials"), ReflectEmpty="anonymous", ReflectInvalid="anonymous"] attribute DOMString crossOrigin;
+    [Reflect, ReflectOnly=("anonymous","use-credentials"), ReflectEmpty="anonymous", ReflectInvalid="anonymous"] attribute DOMString? crossOrigin;

[arv (Not doing code reviews), 2014/09/03 01:16:03]

How does ReflectEmpty work here?

[sof, 2014/09/03 18:30:57]

The concepts could be stratified more clearly, but [ReflectEmpty] handles the
mapping from the empty content attribute keyword value, <foo crossorigin>, onto
the attribute state "anonymous" (which map to the IDL attribute value
"anonymous".)

The CORS setting attribute defines such an empty keyword,

 http://www.whatwg.org/specs/web-apps/current-work/#cors-settings-attribute

[ReflectEmpty] overlaps with the setting of elm.crossOrigin = '', but that's the
only intersection I can think of wrt the spec change here.

Water less muddy?

     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;
 };