Replace many [TreatReturnedNullStringAs=Null] with nullable DOMString

Source/core/dom/Element.idl

 /*
  * Copyright (C) 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 [
     SpecialWrapFor=HTMLElement|SVGElement,
 ] interface Element : Node {
 
     // DOM Level 1 Core
 
-    [TreatReturnedNullStringAs=Null] readonly attribute DOMString tagName;
+    readonly attribute DOMString? tagName;
 
-    [TreatReturnedNullStringAs=Null] DOMString getAttribute(DOMString name);
+    DOMString? getAttribute(DOMString name);
     [RaisesException, CustomElementCallbacks] void setAttribute(DOMString name, DOMString value);
     [CustomElementCallbacks] void removeAttribute(DOMString name);
     [MeasureAs=ElementGetAttributeNode] Attr getAttributeNode([Default=Undefined] optional DOMString name); // Removed from DOM4.
     [RaisesException, CustomElementCallbacks, MeasureAs=ElementSetAttributeNode] Attr setAttributeNode([Default=Undefined] optional Attr newAttr); // Removed from DOM4.
     [RaisesException, CustomElementCallbacks, MeasureAs=ElementRemoveAttributeNode] Attr removeAttributeNode([Default=Undefined] optional Attr oldAttr); // Removed from DOM4.
     HTMLCollection getElementsByTagName(DOMString name);
 
     [PerWorldBindings, ImplementedAs=attributesForBindings] readonly attribute NamedNodeMap     attributes;
     [MeasureAs=HasAttributes] boolean hasAttributes();
 
     // DOM Level 2 Core
 
-    [TreatReturnedNullStringAs=Null] DOMString getAttributeNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString localName);
+    DOMString? getAttributeNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString localName);
     [RaisesException, CustomElementCallbacks] void setAttributeNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString qualifiedName, DOMString value);
     [CustomElementCallbacks] void removeAttributeNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString localName);
     HTMLCollection getElementsByTagNameNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString localName);
     [MeasureAs=ElementGetAttributeNodeNS] Attr getAttributeNodeNS([TreatNullAs=NullString, Default=Undefined] optional DOMString namespaceURI,
                                                                   [Default=Undefined] optional DOMString localName); // Removed from DOM4.
     [RaisesException, CustomElementCallbacks, DeprecateAs=ElementSetAttributeNodeNS] Attr setAttributeNodeNS([Default=Undefined] optional Attr newAttr); // Removed from DOM4.
     boolean hasAttribute(DOMString name);
     boolean hasAttributeNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString localName);
 
     [PerWorldBindings] readonly attribute CSSStyleDeclaration style;
 
     // DOM4
     [Reflect] attribute DOMString id;
-    [TreatReturnedNullStringAs=Null] readonly attribute DOMString namespaceURI;
-    [TreatReturnedNullStringAs=Null, TreatNullAs=NullString, RaisesException=Setter] attribute DOMString prefix;
-    [TreatReturnedNullStringAs=Null] readonly attribute DOMString localName;
+    readonly attribute DOMString? namespaceURI;
+    [RaisesException=Setter] attribute DOMString? prefix;
+    readonly attribute DOMString? localName;
 
     [RaisesException] boolean matches(DOMString selectors);
 
     // Common extensions
 
     readonly attribute long offsetLeft;
     readonly attribute long offsetTop;
     readonly attribute long offsetWidth;
     readonly attribute long offsetHeight;
     [ImplementedAs=offsetParentForBindings, PerWorldBindings] readonly attribute Element offsetParent;
@@ skipping 70 matching lines @@
     [RuntimeEnabled=Touch] attribute EventHandler ontouchend;
     [RuntimeEnabled=Touch] attribute EventHandler ontouchmove;
     [RuntimeEnabled=Touch] attribute EventHandler ontouchstart;
     attribute EventHandler onwebkitfullscreenchange;
     attribute EventHandler onwebkitfullscreenerror;
     attribute EventHandler onwheel;
 };
 
 Element implements ParentNode;
 Element implements ChildNode;