Update more platform classes to use OVERRIDE / FINAL when needed

Source/platform/graphics/filters/FEDisplacementMap.h

 /*
  * Copyright (C) 2004, 2005, 2006, 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005 Rob Buis <buis@kde.org>
  * Copyright (C) 2005 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2013 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 37 matching lines @@
     bool setYChannelSelector(const ChannelSelectorType);
 
     float scale() const;
     bool setScale(float);
 
     virtual void setResultColorSpace(ColorSpace) OVERRIDE;
     virtual void transformResultColorSpace(FilterEffect*, const int) OVERRIDE;
 
     virtual FloatRect mapPaintRect(const FloatRect&, bool forward = true) OVERRIDE FINAL;
 
-    virtual TextStream& externalRepresentation(TextStream&, int indention) const;
+    virtual TextStream& externalRepresentation(TextStream&, int indention) const OVERRIDE;
 
 private:
     FEDisplacementMap(Filter*, ChannelSelectorType xChannelSelector, ChannelSelectorType yChannelSelector, float);
 
     virtual void applySoftware() OVERRIDE;
     virtual bool applySkia() OVERRIDE;
 
     virtual PassRefPtr<SkImageFilter> createImageFilter(SkiaImageFilterBuilder*) OVERRIDE;
 
     ChannelSelectorType m_xChannelSelector;
     ChannelSelectorType m_yChannelSelector;
     float m_scale;
 };
 
 } // namespace WebCore
 
 #endif // FEDisplacementMap_h