Remove dead code related to compositing from Sky

sky/engine/core/rendering/RenderBoxModelObject.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google 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 148 matching lines @@
 
     // Overridden by subclasses to determine line height and baseline position.
     virtual LayoutUnit lineHeight(bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const = 0;
     virtual int baselinePosition(FontBaseline, bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const = 0;
 
     virtual void mapAbsoluteToLocalPoint(MapCoordinatesFlags, TransformState&) const override;
     virtual const RenderObject* pushMappingToContainer(const RenderLayerModelObject* ancestorToStopAt, RenderGeometryMap&) const override;
 
     virtual void setSelectionState(SelectionState) override;
 
-    bool hasAcceleratedCompositing() const;
-
 protected:
     class BackgroundImageGeometry {
     public:
         BackgroundImageGeometry()
             : m_hasNonLocalGeometry(false)
         { }
 
         IntPoint destOrigin() const { return m_destOrigin; }
         void setDestOrigin(const IntPoint& destOrigin)
         {
@@ skipping 103 matching lines @@
     void drawBoxSideFromPath(GraphicsContext*, const LayoutRect&, const Path&, const class BorderEdge[],
                             float thickness, float drawThickness, BoxSide, const RenderStyle*,
                             Color, EBorderStyle, BackgroundBleedAvoidance, bool includeLogicalLeftEdge, bool includeLogicalRightEdge);
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderBoxModelObject, isBoxModelObject());
 
 } // namespace blink
 
 #endif  // SKY_ENGINE_CORE_RENDERING_RENDERBOXMODELOBJECT_H_