Implement incremental paint property tree rebuilding

third_party/WebKit/Source/platform/graphics/paint/ClipPaintPropertyNode.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 ClipPaintPropertyNode_h
 #define ClipPaintPropertyNode_h
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/FloatRoundedRect.h"
 #include "platform/graphics/paint/TransformPaintPropertyNode.h"
@@ skipping 36 matching lines @@
 
   const TransformPaintPropertyNode* localTransformSpace() const {
     return m_localTransformSpace.get();
   }
   const FloatRoundedRect& clipRect() const { return m_clipRect; }
 
   // Reference to inherited clips, or nullptr if this is the only clip.
   const ClipPaintPropertyNode* parent() const { return m_parent.get(); }
   bool isRoot() const { return !m_parent; }
 
+#if DCHECK_IS_ON()
+  // The clone function is used by FindPropertiesNeedingUpdate.h for recording
+  // a clip node before it has been updated, to later detect changes.
+  PassRefPtr<ClipPaintPropertyNode> clone() const {
+    return adoptRef(
+        new ClipPaintPropertyNode(m_parent, m_localTransformSpace, m_clipRect));
+  }
+
+  // The equality operator is used by FindPropertiesNeedingUpdate.h for checking
+  // if a clip node has changed.
+  bool operator==(const ClipPaintPropertyNode& o) const {
+    return m_parent == o.m_parent &&
+           m_localTransformSpace == o.m_localTransformSpace &&
+           m_clipRect == o.m_clipRect;
+  }
+#endif
+
  private:
   ClipPaintPropertyNode(
       PassRefPtr<const ClipPaintPropertyNode> parent,
       PassRefPtr<const TransformPaintPropertyNode> localTransformSpace,
       const FloatRoundedRect& clipRect)
       : m_parent(parent),
         m_localTransformSpace(localTransformSpace),
         m_clipRect(clipRect) {}
 
   RefPtr<const ClipPaintPropertyNode> m_parent;
   RefPtr<const TransformPaintPropertyNode> m_localTransformSpace;
   FloatRoundedRect m_clipRect;
 };
 
 // Redeclared here to avoid ODR issues.
 // See platform/testing/PaintPrinters.h.
 void PrintTo(const ClipPaintPropertyNode&, std::ostream*);
 
 }  // namespace blink
 
 #endif  // ClipPaintPropertyNode_h