Implement incremental paint property tree rebuilding

third_party/WebKit/Source/platform/graphics/paint/TransformPaintPropertyNode.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 TransformPaintPropertyNode_h
 #define TransformPaintPropertyNode_h
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/FloatPoint3D.h"
 #include "platform/transforms/TransformationMatrix.h"
@@ skipping 51 matching lines @@
   // accumulated transform from its ancestors.
   bool flattensInheritedTransform() const {
     return m_flattensInheritedTransform;
   }
 
   // Content whose transform nodes have a common rendering context ID are 3D
   // sorted. If this is 0, content will not be 3D sorted.
   unsigned renderingContextID() const { return m_renderingContextID; }
   bool hasRenderingContext() const { return m_renderingContextID; }
 
+#if DCHECK_IS_ON()
+  // The clone function is used by FindPropertiesNeedingUpdate.h for recording
+  // a transform node before it has been updated, to later detect changes.
+  PassRefPtr<TransformPaintPropertyNode> clone() const {
+    return adoptRef(new TransformPaintPropertyNode(m_matrix, m_origin, m_parent,
+                                                   m_flattensInheritedTransform,
+                                                   m_renderingContextID));
+  }
+
+  // The equality operator is used by FindPropertiesNeedingUpdate.h for checking
+  // if a transform node has changed.
+  bool operator==(const TransformPaintPropertyNode& o) const {
+    return m_matrix == o.m_matrix && m_origin == o.m_origin &&
+           m_parent == o.m_parent &&
+           m_flattensInheritedTransform == o.m_flattensInheritedTransform &&
+           m_renderingContextID == o.m_renderingContextID;
+  }
+#endif
+
  private:
   TransformPaintPropertyNode(
       const TransformationMatrix& matrix,
       const FloatPoint3D& origin,
       PassRefPtr<const TransformPaintPropertyNode> parent,
       bool flattensInheritedTransform,
       unsigned renderingContextID)
       : m_matrix(matrix),
         m_origin(origin),
         m_parent(parent),
         m_flattensInheritedTransform(flattensInheritedTransform),
         m_renderingContextID(renderingContextID) {}
 
   TransformationMatrix m_matrix;
   FloatPoint3D m_origin;
   RefPtr<const TransformPaintPropertyNode> m_parent;
   bool m_flattensInheritedTransform;
   unsigned m_renderingContextID;
 };
 
 // Redeclared here to avoid ODR issues.
 // See platform/testing/PaintPrinters.h.
 void PrintTo(const TransformPaintPropertyNode&, std::ostream*);
 
 }  // namespace blink
 
 #endif  // TransformPaintPropertyNode_h