Remove TreatNullAs=NullString for HTMLButtonElement

Source/core/html/HTMLButtonElement.idl

Index: Source/core/html/HTMLButtonElement.idl
diff --git a/Source/core/html/HTMLButtonElement.idl b/Source/core/html/HTMLButtonElement.idl
index 0fef1611242433af557f68c5f2684cef673956e0..db8c147a560189eb3f9b566f85ca7e6f1d264e9c 100644
--- a/Source/core/html/HTMLButtonElement.idl
+++ b/Source/core/html/HTMLButtonElement.idl
@@ -22,14 +22,14 @@ interface HTMLButtonElement : HTMLElement {
     [Reflect] attribute boolean autofocus;
     [Reflect] attribute boolean disabled;
     readonly attribute HTMLFormElement form;
-    [Reflect, TreatNullAs=NullString, URL, PerWorldBindings, ActivityLogging=SetterForIsolatedWorlds] attribute DOMString formAction;
-    [TreatNullAs=NullString] attribute DOMString formEnctype;
-    [TreatNullAs=NullString] attribute DOMString formMethod;
+    [Reflect, URL, PerWorldBindings, ActivityLogging=SetterForIsolatedWorlds] attribute DOMString formAction;
+    attribute DOMString formEnctype;
+    attribute DOMString formMethod;
     [Reflect] attribute boolean formNoValidate;
-    [Reflect, TreatNullAs=NullString] attribute DOMString formTarget;
-    [Reflect, TreatNullAs=NullString] attribute DOMString name;
-    [TreatNullAs=NullString] attribute DOMString type;
-    [Reflect, TreatNullAs=NullString] attribute DOMString value;
+    [Reflect] attribute DOMString formTarget;
+    [Reflect] attribute DOMString name;
+    attribute DOMString type;
+    [Reflect] attribute DOMString value;
 
     readonly attribute boolean willValidate;
     readonly attribute ValidityState validity;