Introduce EditingAlgorithm<Traversal> class

Source/core/editing/htmlediting.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007 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 346 matching lines @@
     LayoutObject* renderer = enclosingBlockElement->layoutObject();
     return renderer ? renderer->style()->direction() : LTR;
 }
 
 // This method is used to create positions in the DOM. It returns the maximum valid offset
 // in a node. It returns 1 for some elements even though they do not have children, which
 // creates technically invalid DOM Positions. Be sure to call parentAnchoredEquivalent
 // on a Position before using it to create a DOM Range, or an exception will be thrown.
 int lastOffsetForEditing(const Node* node)
 {
-    ASSERT(node);
-    if (!node)
-        return 0;
-    if (node->offsetInCharacters())
-        return node->maxCharacterOffset();
-
-    if (node->hasChildren())
-        return node->countChildren();
-
-    // NOTE: This should preempt the childNodeCount for, e.g., select nodes
-    if (editingIgnoresContent(node))
-        return 1;
-
-    return 0;
+    return EditingStrategy::lastOffsetForEditing(node);
 }
 
 String stringWithRebalancedWhitespace(const String& string, bool startIsStartOfParagraph, bool endIsEndOfParagraph)
 {
     unsigned length = string.length();
 
     StringBuilder rebalancedString;
     rebalancedString.reserveCapacity(length);
 
     bool previousCharacterWasSpace = false;
@@ skipping 804 matching lines @@
     // if the selection starts just before a paragraph break, skip over it
     if (isEndOfParagraph(visiblePosition))
         return visiblePosition.next().deepEquivalent().downstream();
 
     // otherwise, make sure to be at the start of the first selected node,
     // instead of possibly at the end of the last node before the selection
     return visiblePosition.deepEquivalent().downstream();
 }
 
 } // namespace blink