Make [TreatNullAs=NullString] DOMString arguments nullable instead

Source/core/dom/Document.idl

Index: Source/core/dom/Document.idl
diff --git a/Source/core/dom/Document.idl b/Source/core/dom/Document.idl
index 8be394b7d3cc56dd8c07c9ea760f4fb9ec712a77..46fec3bf92259e905f80e67af41732479596e1d6 100644
--- a/Source/core/dom/Document.idl
+++ b/Source/core/dom/Document.idl
@@ -43,10 +43,10 @@ typedef (CanvasRenderingContext2D or WebGLRenderingContext) RenderingContext;
     // Introduced in DOM Level 2:
 
     [CustomElementCallbacks, RaisesException, TypeChecking=Interface] Node importNode(Node node, optional boolean deep);
-    [CustomElementCallbacks, RaisesException] Element createElementNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString qualifiedName);
-    [RaisesException, DeprecateAs=DocumentCreateAttributeNS] Attr createAttributeNS([TreatNullAs=NullString,Default=Undefined] optional DOMString namespaceURI,
-                                                                                  [TreatNullAs=NullString,Default=Undefined] optional DOMString qualifiedName); // Removed from DOM4.
-    HTMLCollection getElementsByTagNameNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString localName);
+    [CustomElementCallbacks, RaisesException] Element createElementNS(DOMString? namespaceURI, DOMString qualifiedName);
+    [RaisesException, DeprecateAs=DocumentCreateAttributeNS] Attr createAttributeNS([Default=Undefined] optional DOMString? namespaceURI,
+                                                                                    [Default=Undefined] optional DOMString? qualifiedName); // Removed from DOM4.
+    HTMLCollection getElementsByTagNameNS(DOMString? namespaceURI, DOMString localName);
     [PerWorldBindings] Element getElementById(DOMString elementId);
 
     // DOM Level 3 Core
@@ -205,9 +205,8 @@ typedef (CanvasRenderingContext2D or WebGLRenderingContext) RenderingContext;
     [RuntimeEnabled=Touch] TouchList createTouchList(Touch... touches);
 
     [CallWith=ScriptState, CustomElementCallbacks, RaisesException, MeasureAs=DocumentRegisterElement] CustomElementConstructor registerElement(DOMString name, optional Dictionary options);
-    [CustomElementCallbacks, PerWorldBindings, RaisesException] Element createElement(DOMString localName, [TreatNullAs=NullString] DOMString typeExtension);
-    [CustomElementCallbacks, RaisesException] Element createElementNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString qualifiedName,
-                            [TreatNullAs=NullString] DOMString typeExtension);
+    [CustomElementCallbacks, PerWorldBindings, RaisesException] Element createElement(DOMString localName, DOMString? typeExtension);
+    [CustomElementCallbacks, RaisesException] Element createElementNS(DOMString? namespaceURI, DOMString qualifiedName, DOMString? typeExtension);
 
     // Page visibility API.
     readonly attribute DOMString visibilityState;