Move LayoutBoxModelObject's PaintLayer member to rare paint data

third_party/WebKit/Source/core/paint/RarePaintData.h

 // Copyright 2017 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 RarePaintData_h
 #define RarePaintData_h
 
 #include "core/CoreExport.h"
 #include "wtf/Allocator.h"
 #include "wtf/Noncopyable.h"
 
 namespace blink {
 
 class PropertyTreeState;
 class ObjectPaintProperties;
+class PaintLayer;
 
 // This is for paint-related data on LayoutObject that is not needed on all
 // objects.
-// TODO(pdr): Store LayoutBoxModelObject's m_paintLayer in this structure.
 class CORE_EXPORT RarePaintData {
   WTF_MAKE_NONCOPYABLE(RarePaintData);
   USING_FAST_MALLOC(RarePaintData);
 
  public:
   RarePaintData();
   ~RarePaintData();
 
+  PaintLayer* Layer() { return layer_.get(); }
+  void SetLayer(std::unique_ptr<PaintLayer>);
+
   ObjectPaintProperties* PaintProperties() const {
     return paint_properties_.get();
   }
   ObjectPaintProperties& EnsurePaintProperties();
 
   PropertyTreeState* LocalBorderBoxProperties() const {
     return local_border_box_properties_.get();
   }
 
   void ClearLocalBorderBoxProperties();
   void SetLocalBorderBoxProperties(PropertyTreeState&);
 
   // This is the complete set of property nodes that can be used to paint the
   // contents of this object. It is similar to local_border_box_properties_ but
   // includes properties (e.g., overflow clip, scroll translation) that apply
   // to contents.
   PropertyTreeState ContentsProperties() const;
 
  private:
+  // The PaintLayer associated with this LayoutBoxModelObject. This can be null
+  // depending on the return value of LayoutBoxModelObject::layerTypeRequired().
+  std::unique_ptr<PaintLayer> layer_;
+
   // Holds references to the paint property nodes created by this object.
   std::unique_ptr<ObjectPaintProperties> paint_properties_;
 
   // This is a complete set of property nodes that should be used as a
   // starting point to paint a LayoutObject. This data is cached because some
   // properties inherit from the containing block chain instead of the
   // painting parent and cannot be derived in O(1) during the paint walk.
   //
   // For example: <div style='opacity: 0.3;'/>
   //   The div's local border box properties would have an opacity 0.3 effect
   //   node. Even though the div has no transform, its local border box
   //   properties would have a transform node that points to the div's
   //   ancestor transform space.
   std::unique_ptr<PropertyTreeState> local_border_box_properties_;
 };
 
 }  // namespace blink
 
 #endif