Improve code readibility of PaintPropertyTreeBuilder

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"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
 
 #include <iosfwd>
 
 namespace blink {
 
 // A transform created by a css property such as "transform" or "perspective"
 // along with a reference to the parent TransformPaintPropertyNode, or nullptr
 // for the root.
 class PLATFORM_EXPORT TransformPaintPropertyNode : public RefCounted<TransformPaintPropertyNode> {
 public:
     static PassRefPtr<TransformPaintPropertyNode> create(
-        PassRefPtr<TransformPaintPropertyNode> parent,
+        PassRefPtr<const TransformPaintPropertyNode> parent,
         const TransformationMatrix& matrix,
         const FloatPoint3D& origin,
         bool flattensInheritedTransform = false,
         unsigned renderingContextID = 0)
     {
         return adoptRef(new TransformPaintPropertyNode(matrix, origin, parent, flattensInheritedTransform, renderingContextID));
     }
 
-    void update(PassRefPtr<TransformPaintPropertyNode> parent, const TransformationMatrix& matrix, const FloatPoint3D& origin, bool flattensInheritedTransform = false, unsigned renderingContextID = 0)
+    void update(PassRefPtr<const TransformPaintPropertyNode> parent, const TransformationMatrix& matrix, const FloatPoint3D& origin, bool flattensInheritedTransform = false, unsigned renderingContextID = 0)
     {
         m_parent = parent;
         m_matrix = matrix;
         m_origin = origin;
         m_flattensInheritedTransform = flattensInheritedTransform;
         m_renderingContextID = 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.
-    TransformPaintPropertyNode* parent() const { return m_parent.get(); }
+    const TransformPaintPropertyNode* parent() const { return m_parent.get(); }
 
     // If true, content with this transform node (or its descendant) appears in
     // the plane of its parent. This is implemented by flattening the total
     // 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; }
 
 private:
     TransformPaintPropertyNode(
         const TransformationMatrix& matrix,
         const FloatPoint3D& origin,
-        PassRefPtr<TransformPaintPropertyNode> parent,
+        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<TransformPaintPropertyNode> m_parent;
+    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