Introduce use counters for shadow DOM handling in plainText()

Source/core/editing/iterators/TextIterator.h

 /*
  * Copyright (C) 2004, 2006, 2009 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 160 matching lines @@
     // Used when text boxes are out of order (Hebrew/Arabic w/ embeded LTR text)
     Vector<InlineTextBox*> m_sortedTextBoxes;
     size_t m_sortedTextBoxesPosition;
 
     const TextIteratorBehaviorFlags m_behavior;
 
     // Used when deciding text fragment created by :first-letter should be looked into.
     bool m_handledFirstLetter;
     // Used when stopsOnFormControls() is true to determine if the iterator should keep advancing.
     bool m_shouldStop;
+    // Used for use counter |InnerTextWithShadowTree| and
+    // |SelectionToStringWithShadowTree|, we should not use other purpose.
+    bool m_handleShadowRoot;
 
     // Contains state of emitted text.
     TextIteratorTextState m_textState;
 };
 
 extern template class CORE_EXTERN_TEMPLATE_EXPORT TextIteratorAlgorithm<EditingStrategy>;
 extern template class CORE_EXTERN_TEMPLATE_EXPORT TextIteratorAlgorithm<EditingInComposedTreeStrategy>;
 
 using TextIterator = TextIteratorAlgorithm<EditingStrategy>;
 using TextIteratorInComposedTree = TextIteratorAlgorithm<EditingInComposedTreeStrategy>;
 
 } // namespace blink
 
 #endif // TextIterator_h