Move LayoutBoxModelObject's PaintLayer member to rare paint data

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

Index: third_party/WebKit/Source/core/paint/RarePaintData.cpp
diff --git a/third_party/WebKit/Source/core/paint/RarePaintData.cpp b/third_party/WebKit/Source/core/paint/RarePaintData.cpp
index d3591ae2e6577bdb404f54ad1d6b6ed8cbdb4a45..0a2ec1f22cb621c7e92f244cb48100a9c9d65e65 100644
--- a/third_party/WebKit/Source/core/paint/RarePaintData.cpp
+++ b/third_party/WebKit/Source/core/paint/RarePaintData.cpp
@@ -5,6 +5,7 @@
 #include "core/paint/RarePaintData.h"
 
 #include "core/paint/ObjectPaintProperties.h"
+#include "core/paint/PaintLayer.h"
 
 namespace blink {
 
@@ -12,6 +13,10 @@ RarePaintData::RarePaintData() {}
 
 RarePaintData::~RarePaintData() {}
 
+void RarePaintData::SetLayer(std::unique_ptr<PaintLayer> layer) {
+  layer_ = std::move(layer);
+};
+
 ObjectPaintProperties& RarePaintData::EnsurePaintProperties() {
   if (!paint_properties_)
     paint_properties_ = ObjectPaintProperties::Create();