Implement incremental paint property tree rebuilding

third_party/WebKit/Source/platform/graphics/paint/EffectPaintPropertyNode.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef EffectPaintPropertyNode_h
 #define EffectPaintPropertyNode_h
 
 #include "platform/PlatformExport.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
@@ skipping 19 matching lines @@
     return adoptRef(new EffectPaintPropertyNode(std::move(parent), opacity));
   }
 
   void update(PassRefPtr<const EffectPaintPropertyNode> parent, float opacity) {
     DCHECK(!isRoot());
     DCHECK(parent != this);
     m_parent = parent;
     m_opacity = opacity;
   }
 
+  PassRefPtr<EffectPaintPropertyNode> clone() const {
+    return adoptRef(new EffectPaintPropertyNode(m_parent, m_opacity));
+  }
+
+  bool operator==(const EffectPaintPropertyNode& o) const {
+    return m_parent == o.m_parent && m_opacity == o.m_opacity;
+  }
+
   float opacity() const { return m_opacity; }
 
   // Parent effect or nullptr if this is the root effect.
   const EffectPaintPropertyNode* parent() const { return m_parent.get(); }
   bool isRoot() const { return !m_parent; }
 
  private:
   EffectPaintPropertyNode(PassRefPtr<const EffectPaintPropertyNode> parent,
                           float opacity)
       : m_parent(parent), m_opacity(opacity) {}
 
   RefPtr<const EffectPaintPropertyNode> m_parent;
   float m_opacity;
 };
 
 // Redeclared here to avoid ODR issues.
 // See platform/testing/PaintPrinters.h.
 void PrintTo(const EffectPaintPropertyNode&, std::ostream*);
 
 }  // namespace blink
 
 #endif  // EffectPaintPropertyNode_h