Make FrameCaret contains CaretBase instead of deriving from it

third_party/WebKit/Source/core/editing/DragCaretController.h

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights
  * reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 11 matching lines @@
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef DragCaretController_h
 #define DragCaretController_h
 
 #include "core/dom/SynchronousMutationObserver.h"
 #include "core/editing/CaretBase.h"
+#include <memory>
 
 namespace blink {
 
 class DragCaretController final
     : public GarbageCollectedFinalized<DragCaretController>,
       public SynchronousMutationObserver {
   WTF_MAKE_NONCOPYABLE(DragCaretController);
   USING_GARBAGE_COLLECTED_MIXIN(DragCaretController);
 
  public:
@@ skipping 17 matching lines @@
   DragCaretController();
 
   // Implementations of |SynchronousMutationObserver|
   void nodeChildrenWillBeRemoved(ContainerNode&) final;
   void nodeWillBeRemoved(Node&) final;
 
   PositionWithAffinity m_position;
   // caret rect in coords local to the layoutObject responsible for painting the
   // caret
   LayoutRect m_caretLocalRect;
-  const Member<CaretBase> m_caretBase;
+  const std::unique_ptr<CaretBase> m_caretBase;
 };
 
 }  // namespace blink
 
 #endif  // DragCaretController_h