Drop some dead code from FilterEffect

Source/platform/graphics/filters/FEFlood.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 23 matching lines @@
 
     Color floodColor() const;
     bool setFloodColor(const Color &);
 
     float floodOpacity() const;
     bool setFloodOpacity(float);
 
     // feFlood does not perform color interpolation of any kind, so the result is always in the current
     // color space regardless of the value of color-interpolation-filters.
     virtual void setOperatingColorSpace(ColorSpace) override { }
-    virtual void setResultColorSpace(ColorSpace) override { }
 
     virtual PassRefPtr<SkImageFilter> createImageFilter(SkiaImageFilterBuilder*) override;
 
     virtual TextStream& externalRepresentation(TextStream&, int indention) const override;
 
 private:
     FEFlood(Filter*, const Color&, float);
 
     Color m_floodColor;
     float m_floodOpacity;
 };
 
 } // namespace blink
 
 #endif // FEFlood_h