Reland of "Tracking reference filter mutation via SVGElementProxy"

third_party/WebKit/Source/core/layout/svg/LayoutSVGResourceFilter.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) 2009 Dirk Schulze <krit@webkit.org>
  * Copyright (C) Research In Motion Limited 2010. 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
@@ skipping 86 matching lines @@
   }
   void setFilterDataForLayoutObject(LayoutObject* object,
                                     FilterData* filterData) {
     m_filter.set(object, filterData);
   }
 
  protected:
   void willBeDestroyed() override;
 
  private:
+  SVGElementProxySet* elementProxySet() override;
+
   void disposeFilterMap();
 
   using FilterMap = PersistentHeapHashMap<LayoutObject*, Member<FilterData>>;
   FilterMap m_filter;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutSVGResourceFilter, isSVGResourceFilter());
 
 }  // namespace blink
 
 #endif