Add a constructor to TextIterator taking two Positions as iteration range.

Source/core/editing/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 69 matching lines @@
     Vector<unsigned, 1> m_words;
 };
 
 // Iterates through the DOM range, returning all the text, and 0-length boundaries
 // at points where replaced elements break up the text flow.  The text comes back in
 // chunks so as to optimize for performance of the iteration.
 
 class TextIterator {
 public:
     explicit TextIterator(const Range*, TextIteratorBehaviorFlags = TextIteratorDefaultBehavior);
+    // [start, end] indicates the document range that the iteration should take place within (both ends inclusive).
+    TextIterator(const Position& start, const Position& end, TextIteratorBehaviorFlags = TextIteratorDefaultBehavior);
     ~TextIterator();
 
     bool atEnd() const { return !m_positionNode || m_shouldStop; }
     void advance();
 
     int length() const { return m_textLength; }
     UChar characterAt(unsigned index) const;
     String substring(unsigned position, unsigned length) const;
     void appendTextToStringBuilder(StringBuilder&, unsigned position = 0, unsigned maxLength = UINT_MAX) const;
 
@@ skipping 21 matching lines @@
 
 private:
     enum IterationProgress {
         HandledNone,
         HandledAuthorShadowRoots,
         HandledUserAgentShadowRoot,
         HandledNode,
         HandledChildren
     };
 
+    void initialize(const Position& start, const Position& end);
+
     int startOffset() const { return m_positionStartOffset; }
     const String& string() const { return m_text; }
     void exitNode();
     bool shouldRepresentNodeOffsetZero();
     bool shouldEmitSpaceBeforeAndAfterNode(Node*);
     void representNodeOffsetZero();
     bool handleTextNode();
     bool handleReplacedElement();
     bool handleNonTextNode();
     void handleTextBox();
@@ skipping 222 matching lines @@
     Vector<UChar> m_buffer;
     // Did we have to look ahead in the textIterator to confirm the current chunk?
     bool m_didLookAhead;
     RefPtr<Range> m_range;
     TextIterator m_textIterator;
 };
 
 }
 
 #endif