Make 'crossOrigin' IDL attributes nullable

Source/core/html/HTMLImageElement.idl

Index: Source/core/html/HTMLImageElement.idl
diff --git a/Source/core/html/HTMLImageElement.idl b/Source/core/html/HTMLImageElement.idl
index 98ae54aeec662e9daf33e9ca76467df84c9e0d44..cde8092146bd3d4fd29ec5d562d55d36105c97ca 100644
--- a/Source/core/html/HTMLImageElement.idl
+++ b/Source/core/html/HTMLImageElement.idl
@@ -28,7 +28,7 @@
     [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;