Adds filter support for offscreen canvas

third_party/WebKit/Source/core/paint/FilterEffectBuilder.h

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 31 matching lines @@
 class FloatRect;
 class Node;
 class ReferenceFilterOperation;
 class SVGFilterElement;
 class SVGFilterGraphNodeMap;
 
 class CORE_EXPORT FilterEffectBuilder final {
   STACK_ALLOCATED();
 
  public:
+  FilterEffectBuilder(const FloatRect& zoomedReferenceBox,
+                      float zoom,
+                      const SkPaint* fillPaint = nullptr,
+                      const SkPaint* strokePaint = nullptr);
   FilterEffectBuilder(Node*,
                       const FloatRect& zoomedReferenceBox,
                       float zoom,
                       const SkPaint* fillPaint = nullptr,
                       const SkPaint* strokePaint = nullptr);
 
   Filter* buildReferenceFilter(SVGFilterElement&,
                                FilterEffect* previousEffect,
                                SVGFilterGraphNodeMap* = nullptr) const;
 
   FilterEffect* buildFilterEffect(const FilterOperations&) const;
   CompositorFilterOperations buildFilterOperations(
       const FilterOperations&) const;
 
  private:
   Filter* buildReferenceFilter(const ReferenceFilterOperation&,
                                FilterEffect* previousEffect) const;
 
   Member<Node> m_targetContext;
   FloatRect m_referenceBox;
   float m_zoom;
   const SkPaint* m_fillPaint;
   const SkPaint* m_strokePaint;
 };
 
 }  // namespace blink
 
 #endif  // FilterEffectBuilder_h