Remove the CSSOM.

sky/engine/core/css/CSSComputedStyleDeclaration.h

 /*
  * Copyright (C) 2004 Zack Rusin <zack@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2008, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser 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,
@@ skipping 57 matching lines @@
     PassRefPtr<CSSValue> getPropertyCSSValue(CSSPropertyID, EUpdateLayout = UpdateLayout) const;
     PassRefPtr<CSSValue> getFontSizeCSSValuePreferringKeyword() const;
     FixedPitchFontType fixedPitchFontType() const;
 
     PassRefPtr<MutableStylePropertySet> copyPropertiesInSet(const Vector<CSSPropertyID>&) const;
 
 private:
     CSSComputedStyleDeclaration(PassRefPtr<Node>, bool allowVisitedStyle, const String&);
 
     // CSSOM functions. Don't make these public.
-    virtual CSSRule* parentRule() const override;
     virtual unsigned length() const override;
     virtual String item(unsigned index) const override;
     PassRefPtr<RenderStyle> computeRenderStyle(CSSPropertyID) const;
     virtual PassRefPtr<CSSValue> getPropertyCSSValue(const String& propertyName) override;
     virtual String getPropertyValue(const String& propertyName) override;
     virtual String getPropertyPriority(const String& propertyName) override;
     virtual String getPropertyShorthand(const String& propertyName) override;
     virtual bool isPropertyImplicit(const String& propertyName) override;
     virtual void setProperty(const String& propertyName, const String& value, const String& priority, ExceptionState&) override;
     virtual String removeProperty(const String& propertyName, ExceptionState&) override;
@@ skipping 19 matching lines @@
     PseudoId m_pseudoElementSpecifier;
     bool m_allowVisitedStyle;
 #if !ENABLE(OILPAN)
     unsigned m_refCount;
 #endif
 };
 
 } // namespace blink
 
 #endif  // SKY_ENGINE_CORE_CSS_CSSCOMPUTEDSTYLEDECLARATION_H_