Support display: contents for elements, first-line and first-letter pseudos.

third_party/WebKit/Source/core/html/HTMLOptGroupElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2010 Apple Inc. All rights reserved.
  *
  * 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.
@@ skipping 37 matching lines @@
 
  private:
   explicit HTMLOptGroupElement(Document&);
 
   bool supportsFocus() const override;
   void parseAttribute(const QualifiedName&,
                       const AtomicString&,
                       const AtomicString&) override;
   void accessKeyAction(bool sendMouseEvents) override;
   void didAddUserAgentShadowRoot(ShadowRoot&) override;
-  void attachLayoutTree(const AttachContext& = AttachContext()) override;
-  void detachLayoutTree(const AttachContext& = AttachContext()) override;
   bool matchesEnabledPseudoClass() const override;
   InsertionNotificationRequest insertedInto(ContainerNode*) override;
   void removedFrom(ContainerNode*) override;
 
-  // <optgroup> might not have a layoutObject so we manually manage a cached
-  // style.
-  void updateNonComputedStyle();
-  ComputedStyle* nonLayoutObjectComputedStyle() const override;
   PassRefPtr<ComputedStyle> customStyleForLayoutObject() override;
 
   void updateGroupLabel();
-
-  RefPtr<ComputedStyle> m_style;
 };
 
 }  // namespace blink
 
 #endif  // HTMLOptGroupElement_h