Alternate approach to updating paint property nodes

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 16 matching lines @@
     }
 
     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.
     TransformPaintPropertyNode* parent() const { return m_parent.get(); }
 
 private:
-
     TransformPaintPropertyNode(const TransformationMatrix& matrix, const FloatPoint3D& origin, PassRefPtr<TransformPaintPropertyNode> parent)
         : m_matrix(matrix), m_origin(origin), m_parent(parent) { }
 
-    const TransformationMatrix m_matrix;
-    const FloatPoint3D m_origin;
+    friend class PaintPropertyTreeBuilder;
+    // These setters should only be used by PaintPropertyTreeBuilder.
+    void setMatrix(const TransformationMatrix& matrix) { m_matrix = matrix; }
+    void setOrigin(const FloatPoint3D& origin) { m_origin = origin; }
+    void setParent(PassRefPtr<TransformPaintPropertyNode> parent) { m_parent = parent; }
+
+    TransformationMatrix m_matrix;
+    FloatPoint3D m_origin;
     RefPtr<TransformPaintPropertyNode> m_parent;
 };
 
 // Redeclared here to avoid ODR issues.
 // See platform/testing/PaintPrinters.h.
 void PrintTo(const TransformPaintPropertyNode&, std::ostream*);
 
 } // namespace blink
 
 #endif // TransformPaintPropertyNode_h