Sync the HTMLElement interface with the spec

Source/core/html/HTMLElement.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.
  */
 
+// https://html.spec.whatwg.org/#htmlelement
+
 interface HTMLElement : Element {
+    // metadata attributes
     [Reflect] attribute DOMString title;
     [Reflect] attribute DOMString lang;
     attribute boolean translate;
     attribute DOMString dir;
+    // FIXME: dataset is on Element.
 
-    [CustomElementCallbacks] attribute long              tabIndex;
-    [CustomElementCallbacks] attribute boolean           draggable;
-    [Reflect, TreatNullAs=NullString, MeasureAs=PrefixedHTMLElementDropzone] attribute DOMString webkitdropzone;
+    // user interaction
     [Reflect] attribute boolean hidden;
+    void click();
+    [CustomElementCallbacks] attribute long tabIndex;
+    // FIXME: focus() and blur() are on Element.
     [Reflect] attribute DOMString accessKey;
+    [CustomElementCallbacks] attribute boolean draggable;
+    [RuntimeEnabled=ContextMenu] attribute HTMLMenuElement? contextMenu;
+    attribute boolean spellcheck;
 
-    // Extensions
+    // HTMLElement implements ElementContentEditable
+    // https://html.spec.whatwg.org/#contenteditable
+    [CustomElementCallbacks, RaisesException=Setter] attribute DOMString contentEditable;
+    readonly attribute boolean isContentEditable;
+
+    // Input Method Editor API
+    // https://dvcs.w3.org/hg/ime-api/raw-file/default/Overview.html#the-inputmethodcontext-property
+    [RuntimeEnabled=IMEAPI] readonly attribute InputMethodContext? inputMethodContext;
+
+    // Non-standard APIs
     [TreatNullAs=NullString, CustomElementCallbacks, RaisesException=Setter, MeasureAs=HTMLElementInnerText] attribute DOMString innerText;
     [TreatNullAs=NullString, CustomElementCallbacks, RaisesException=Setter, MeasureAs=HTMLElementOuterText] attribute DOMString outerText;
-
-    [RuntimeEnabled=IMEAPI] readonly attribute InputMethodContext inputMethodContext;
-
-    [CustomElementCallbacks, RaisesException=Setter] attribute DOMString contentEditable;
-    readonly attribute boolean isContentEditable;
-    [RuntimeEnabled=ContextMenu] attribute HTMLMenuElement? contextMenu;
-
-             attribute boolean spellcheck;
-
-    void click();
+    [Reflect, TreatNullAs=NullString, MeasureAs=PrefixedHTMLElementDropzone] attribute DOMString webkitdropzone;
 };
 
 HTMLElement implements GlobalEventHandlers;
-