Add support for [TreatNullAs] extended attribute for reflected attributes

Source/core/html/HTMLAnchorElement.idl

Index: Source/core/html/HTMLAnchorElement.idl
diff --git a/Source/core/html/HTMLAnchorElement.idl b/Source/core/html/HTMLAnchorElement.idl
index 6bb11f95da19a530289109377078058f3598e554..fc3cbac1fb05476dc27ba3cd97d1eddf613cd2c5 100644
--- a/Source/core/html/HTMLAnchorElement.idl
+++ b/Source/core/html/HTMLAnchorElement.idl
@@ -19,18 +19,18 @@
  */
 
 interface HTMLAnchorElement : HTMLElement {
-    [Reflect] attribute DOMString charset;
-    [Reflect] attribute DOMString coords;
-    [Reflect] attribute DOMString download;
-    [Reflect, URL] attribute DOMString href;
-    [Reflect] attribute DOMString hreflang;
-    [Reflect] attribute DOMString name;
-    [Reflect] attribute DOMString ping;
-    [Reflect] attribute DOMString rel;
-    [Reflect] attribute DOMString rev;
-    [Reflect] attribute DOMString shape;
-    [Reflect] attribute DOMString target;
-    [Reflect] attribute DOMString type;
+    [Reflect, TreatNullAs=NullString] attribute DOMString charset;
+    [Reflect, TreatNullAs=NullString] attribute DOMString coords;
+    [Reflect, TreatNullAs=NullString] attribute DOMString download;
+    [Reflect, TreatNullAs=NullString, URL] attribute DOMString href;
+    [Reflect, TreatNullAs=NullString] attribute DOMString hreflang;
+    [Reflect, TreatNullAs=NullString] attribute DOMString name;
+    [Reflect, TreatNullAs=NullString] attribute DOMString ping;
+    [Reflect, TreatNullAs=NullString] attribute DOMString rel;
+    [Reflect, TreatNullAs=NullString] attribute DOMString rev;
+    [Reflect, TreatNullAs=NullString] attribute DOMString shape;
+    [Reflect, TreatNullAs=NullString] attribute DOMString target;
+    [Reflect, TreatNullAs=NullString] attribute DOMString type;
 
     attribute DOMString hash;
     attribute DOMString host;