Preliminary paint property walk implementation for SPv2

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:
-    TransformPaintPropertyNode(const TransformationMatrix& matrix, const FloatPoint3D& origin, PassRefPtr<TransformPaintPropertyNode> parent = nullptr)
+    TransformPaintPropertyNode(const TransformationMatrix& matrix, const FloatPoint3D& origin, TransformPaintPropertyNode* parent = nullptr)

[jbroman, 2015/10/14 15:11:59]

Why this change? PassRefPtr<T> is implicitly constructible from T* (so this
doesn't make callers work that otherwise wouldn't), but this change precludes
passing existing ownership if desired, and makes it less clear that this
constructor owns a reference.

[trchen, 2015/10/14 22:51:13]

You're right. I don't know what I was thinking. Reverted.

         : m_matrix(matrix), m_origin(origin), m_parent(parent) { }
 
     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(); }
 
 private:
     const TransformationMatrix m_matrix;
     const 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