Add support for [TreatNullAs] extended attribute for reflected attributes

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 efd1c6a2f4c8e526dc9b0d044840d01bb17d4f5d..12d8c8f056e36573cdbf96db4d7d7a8284eb562e 100644
--- a/Source/core/html/HTMLImageElement.idl
+++ b/Source/core/html/HTMLImageElement.idl
@@ -20,24 +20,24 @@
 
 [
 ] interface HTMLImageElement : HTMLElement {
-    [Reflect] attribute DOMString name;
-    [Reflect] attribute DOMString align;
-    [Reflect] attribute DOMString alt;
-    [Reflect] attribute DOMString border;
-    [Reflect] attribute DOMString crossOrigin;
+    [Reflect, TreatNullAs=NullString] attribute DOMString name;
+    [Reflect, TreatNullAs=NullString] attribute DOMString align;
+    [Reflect, TreatNullAs=NullString] attribute DOMString alt;
+    [Reflect, TreatNullAs=NullString] attribute DOMString border;
+    [Reflect, TreatNullAs=NullString] attribute DOMString crossOrigin;
     attribute long height;
     [Reflect] attribute long hspace;
     [Reflect] attribute boolean isMap;
-    [Reflect, URL] attribute DOMString longDesc;
-    [Reflect, URL] attribute DOMString src;
-    [Reflect, EnabledAtRuntime=Srcset] attribute DOMString srcset;
-    [Reflect] attribute DOMString useMap;
+    [Reflect, TreatNullAs=NullString, URL] attribute DOMString longDesc;
+    [Reflect, TreatNullAs=NullString, URL] attribute DOMString src;
+    [Reflect, TreatNullAs=NullString, EnabledAtRuntime=Srcset] attribute DOMString srcset;
+    [Reflect, TreatNullAs=NullString] attribute DOMString useMap;
     [Reflect] attribute long vspace;
     attribute long width;
 
     // Extensions
     readonly attribute boolean complete;
-    [Reflect,URL] attribute DOMString lowsrc;
+    [Reflect, TreatNullAs=NullString,URL] attribute DOMString lowsrc;
     readonly attribute long naturalHeight;
     readonly attribute long naturalWidth;
     readonly attribute long x;