Make it possible to custom-paint without an Element.

sky/engine/core/rendering/RenderBox.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007 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 473 matching lines @@
     LayoutUnit computeIntrinsicLogicalContentHeightUsing(const Length& logicalHeightLength, LayoutUnit intrinsicContentHeight, LayoutUnit borderAndPadding) const;
 
     virtual bool shouldComputeSizeAsReplaced() const { return isReplaced() && !isInlineBlock(); }
 
     virtual void mapLocalToContainer(const RenderBox* paintInvalidationContainer, TransformState&, MapCoordinatesFlags = ApplyContainerFlip) const override;
 
     void paintRootBoxFillLayers(const PaintInfo&);
 
     void updateIntrinsicContentLogicalHeight(LayoutUnit intrinsicContentLogicalHeight) const { m_intrinsicContentLogicalHeight = intrinsicContentLogicalHeight; }
 
+    void paintCustomPainting(PaintInfo& paintInfo, const LayoutPoint& paintOffset);
+
 private:
     void updateTransformationMatrix();
     void updateTransform(const RenderStyle* oldStyle);
     void updateFromStyle();
     void updateFilters();
 
     PassRefPtr<HitTestingTransformState> createLocalTransformState(
         RenderLayer* rootLayer, RenderLayer* containerLayer,
         const LayoutRect& hitTestRect, const HitTestLocation& hitTestLocation,
         const HitTestingTransformState* containerTransformState) const;
@@ skipping 110 matching lines @@
         if (UNLIKELY(inlineBoxWrapper() != 0))
             deleteLineBoxWrapper();
     }
 
     ensureRareData().m_inlineBoxWrapper = boxWrapper;
 }
 
 } // namespace blink
 
 #endif  // SKY_ENGINE_CORE_RENDERING_RENDERBOX_H_