Make PaintImages a class and implement a Clone() method.

third_party/WebKit/Source/core/style/StyleRareNonInheritedData.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 19 matching lines @@
 #include "core/css/StyleColor.h"
 #include "core/style/ClipPathOperation.h"
 #include "core/style/ComputedStyleConstants.h"
 #include "core/style/CounterDirectives.h"
 #include "core/style/DataPersistent.h"
 #include "core/style/DataRef.h"
 #include "core/style/FillLayer.h"
 #include "core/style/LineClampValue.h"
 #include "core/style/NinePieceImage.h"
 #include "core/style/OutlineValue.h"
+#include "core/style/PaintImages.h"
 #include "core/style/ShapeValue.h"
 #include "core/style/StyleContentAlignmentData.h"
 #include "core/style/StyleScrollSnapData.h"
 #include "core/style/StyleSelfAlignmentData.h"
 #include "platform/LengthPoint.h"
 #include "platform/graphics/TouchAction.h"
 #include "platform/wtf/PassRefPtr.h"
 #include "platform/wtf/RefCounted.h"
 #include "platform/wtf/Vector.h"
 
@@ skipping 90 matching lines @@
   StyleColor visited_link_text_decoration_color_;
   StyleColor visited_link_background_color_;
   StyleColor visited_link_outline_color_;
   StyleColor visited_link_border_left_color_;
   StyleColor visited_link_border_right_color_;
   StyleColor visited_link_border_top_color_;
   StyleColor visited_link_border_bottom_color_;
 
   Vector<String> callback_selectors_;
 
-  std::unique_ptr<Vector<Persistent<StyleImage>>> paint_images_;
+  std::unique_ptr<PaintImages> paint_images_;
 
   std::unique_ptr<StyleNonInheritedVariables> variables_;
 
   StyleContentAlignmentData align_content_;
   StyleSelfAlignmentData align_items_;
   StyleSelfAlignmentData align_self_;
   StyleContentAlignmentData justify_content_;
   StyleSelfAlignmentData justify_items_;
   StyleSelfAlignmentData justify_self_;
 
@@ skipping 57 matching lines @@
   unsigned has_author_border_ : 1;  // Whether there is a author-defined border.
 
  private:
   StyleRareNonInheritedData();
   StyleRareNonInheritedData(const StyleRareNonInheritedData&);
 };
 
 }  // namespace blink
 
 #endif  // StyleRareNonInheritedData_h