Drop some dead code from FilterEffect

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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #ifndef FEDisplacementMap_h
 #define FEDisplacementMap_h
 
 #include "platform/graphics/filters/FilterEffect.h"
-#include "wtf/text/WTFString.h"
 
 namespace blink {
 
 enum ChannelSelectorType {
     CHANNEL_UNKNOWN = 0,
     CHANNEL_R = 1,
     CHANNEL_G = 2,
     CHANNEL_B = 3,
     CHANNEL_A = 4
 };
 
 class PLATFORM_EXPORT FEDisplacementMap : public FilterEffect {
 public:
     static PassRefPtrWillBeRawPtr<FEDisplacementMap> create(Filter*, ChannelSelectorType xChannelSelector, ChannelSelectorType yChannelSelector, float);
 
     ChannelSelectorType xChannelSelector() const;
     bool setXChannelSelector(const ChannelSelectorType);
 
     ChannelSelectorType yChannelSelector() const;
     bool setYChannelSelector(const ChannelSelectorType);
 
     float scale() const;
     bool setScale(float);
 
-    virtual void setResultColorSpace(ColorSpace) override;
-
     virtual FloatRect mapPaintRect(const FloatRect&, bool forward = true) override final;
 
     virtual TextStream& externalRepresentation(TextStream&, int indention) const override;
 
     FloatRect determineAbsolutePaintRect(const FloatRect& requestedRect) override;
 
 private:
     FEDisplacementMap(Filter*, ChannelSelectorType xChannelSelector, ChannelSelectorType yChannelSelector, float);
 
     virtual PassRefPtr<SkImageFilter> createImageFilter(SkiaImageFilterBuilder*) override;
 
     ChannelSelectorType m_xChannelSelector;
     ChannelSelectorType m_yChannelSelector;
     float m_scale;
 };
 
 } // namespace blink
 
 #endif // FEDisplacementMap_h