Remove TreatNullAs=NullString for HTMLFormElement

LayoutTests/fast/dom/element-attribute-js-null.html

Index: LayoutTests/fast/dom/element-attribute-js-null.html
diff --git a/LayoutTests/fast/dom/element-attribute-js-null.html b/LayoutTests/fast/dom/element-attribute-js-null.html
index 006099e9957307b4c66a7c54081fd19a50caf9b3..585b1f76e6e12c4e11ed039abf076393e083b270 100644
--- a/LayoutTests/fast/dom/element-attribute-js-null.html
+++ b/LayoutTests/fast/dom/element-attribute-js-null.html
@@ -248,13 +248,14 @@
                     type: 'HTMLFormElement',
                     elementToUse: document.createElement('form'),
                     attributes: [
-                        {name: 'name', expectedNull: ''},
-                        {name: 'acceptCharset', expectedNull: ''},
-                        {name: 'action', expectedNull: ''},
-                        {name: 'encoding', expectedNull: 'application/x-www-form-urlencoded'},
+                        {name: 'acceptCharset', expectedNull: 'null'},
+                        {name: 'action', expectedNull: 'null', isUrl: true},
+                        {name: 'autocomplete', expectedNull: 'null'},
                         {name: 'enctype', expectedNull: 'application/x-www-form-urlencoded'},
+                        {name: 'encoding', expectedNull: 'application/x-www-form-urlencoded'},
                         {name: 'method', expectedNull: 'get'},
-                        {name: 'target', expectedNull: ''}
+                        {name: 'name', expectedNull: 'null'},
+                        {name: 'target', expectedNull: 'null'}
                     ]
                 },
                 {