Constify the rendering/ selection code

Source/core/rendering/EllipsisBox.h

 /**
  * Copyright (C) 2003, 2006 Apple Computer, Inc.
  *
  * 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
@@ skipping 31 matching lines @@
 
     virtual void paint(PaintInfo&, const LayoutPoint&, LayoutUnit lineTop, LayoutUnit lineBottom) OVERRIDE;
     virtual bool nodeAtPoint(const HitTestRequest&, HitTestResult&, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, LayoutUnit lineTop, LayoutUnit lineBottom) OVERRIDE;
     void setSelectionState(RenderObject::SelectionState s) { m_selectionState = s; }
     IntRect selectionRect();
 
     virtual float virtualLogicalHeight() const OVERRIDE { return m_height; }
 private:
     void paintMarkupBox(PaintInfo&, const LayoutPoint& paintOffset, LayoutUnit lineTop, LayoutUnit lineBottom, RenderStyle*);
     int height() const { return m_height; }
-    virtual RenderObject::SelectionState selectionState() OVERRIDE { return m_selectionState; }
+    virtual RenderObject::SelectionState selectionState() const OVERRIDE { return m_selectionState; }
     void paintSelection(GraphicsContext*, const FloatPoint&, RenderStyle*, const Font&);
     InlineBox* markupBox() const;
 
     bool m_shouldPaintMarkupBox;
     int m_height;
     AtomicString m_str;
     RenderObject::SelectionState m_selectionState;
 };
 
 } // namespace blink
 
 #endif // EllipsisBox_h