[Editing][CodeHealth] Extract new FrameCaret class from FrameSelection

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

 /*
  * Copyright (C) 2004, 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 81 matching lines @@
     if (!removingNodeRemovesPosition(node, m_position.deepEquivalent()))
         return;
 
     m_position.deepEquivalent().document()->layoutViewItem().clearSelection();
     clear();
 }
 
 DEFINE_TRACE(DragCaretController)
 {
     visitor->trace(m_position);
+    visitor->trace(m_caretBase);
 }
 
 LayoutBlock* DragCaretController::caretLayoutObject() const
 {
     return CaretBase::caretLayoutObject(m_position.deepEquivalent().anchorNode());
 }
 
 bool DragCaretController::isContentEditable() const
 {
     return rootEditableElementOf(m_position);
 }
 
 void DragCaretController::paintDragCaret(LocalFrame* frame, GraphicsContext& context, const LayoutPoint& paintOffset) const
 {
     if (m_position.deepEquivalent().anchorNode()->document().frame() == frame)
         m_caretBase->paintCaret(m_position.deepEquivalent().anchorNode(), context, paintOffset);
 }
 
 } // namespace blink