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 31 matching lines @@
               unsigned renderingContextID = 0) {
     DCHECK(!isRoot());
     DCHECK(parent != this);
     m_parent = parent;
     m_matrix = matrix;
     m_origin = origin;
     m_flattensInheritedTransform = flattensInheritedTransform;
     m_renderingContextID = renderingContextID;
   }
 
+  PassRefPtr<TransformPaintPropertyNode> clone() const {
+    return adoptRef(new TransformPaintPropertyNode(m_matrix, m_origin, m_parent,
+                                                   m_flattensInheritedTransform,
+                                                   m_renderingContextID));
+  }
+
+  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;
+  }
+
   const TransformationMatrix& matrix() const { return m_matrix; }
   const FloatPoint3D& origin() const { return m_origin; }
 
   // Parent transform that this transform is relative to, or nullptr if this
   // is the root transform.
   const TransformPaintPropertyNode* parent() const { return m_parent.get(); }
   bool isRoot() const { return !m_parent; }
 
   // If true, content with this transform node (or its descendant) appears in
   // the plane of its parent. This is implemented by flattening the total
@@ skipping 27 matching lines @@
   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