Introduce nextPositionOf() for VisiblePosition

Source/core/editing/commands/IndentOutdentCommand.cpp

 /*
  * Copyright (C) 2006, 2008 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 202 matching lines @@
 {
     VisiblePosition endOfCurrentParagraph = endOfParagraph(startOfSelection);
     VisiblePosition endOfLastParagraph = endOfParagraph(endOfSelection);
 
     if (endOfCurrentParagraph.deepEquivalent() == endOfLastParagraph.deepEquivalent()) {
         outdentParagraph();
         return;
     }
 
     Position originalSelectionEnd = endingSelection().end();
-    VisiblePosition endAfterSelection = endOfParagraph(endOfLastParagraph.next());
+    VisiblePosition endAfterSelection = endOfParagraph(nextPositionOf(endOfLastParagraph));
 
     while (endOfCurrentParagraph.deepEquivalent() != endAfterSelection.deepEquivalent()) {
-        VisiblePosition endOfNextParagraph = endOfParagraph(endOfCurrentParagraph.next());
+        VisiblePosition endOfNextParagraph = endOfParagraph(nextPositionOf(endOfCurrentParagraph));
         if (endOfCurrentParagraph.deepEquivalent() == endOfLastParagraph.deepEquivalent())
             setEndingSelection(VisibleSelection(originalSelectionEnd, TextAffinity::Downstream));
         else
             setEndingSelection(endOfCurrentParagraph);
 
         outdentParagraph();
 
         // outdentParagraph could move more than one paragraph if the paragraph
         // is in a list item. As a result, endAfterSelection and endOfNextParagraph
         // could refer to positions no longer in the document.
         if (endAfterSelection.isNotNull() && !endAfterSelection.deepEquivalent().inDocument())
             break;
 
         if (endOfNextParagraph.isNotNull() && !endOfNextParagraph.deepEquivalent().inDocument()) {
             endOfCurrentParagraph = VisiblePosition(endingSelection().end());
-            endOfNextParagraph = endOfParagraph(endOfCurrentParagraph.next());
+            endOfNextParagraph = endOfParagraph(nextPositionOf(endOfCurrentParagraph));
         }
         endOfCurrentParagraph = endOfNextParagraph;
     }
 }
 
 void IndentOutdentCommand::formatSelection(const VisiblePosition& startOfSelection, const VisiblePosition& endOfSelection)
 {
     if (m_typeOfAction == Indent)
         ApplyBlockElementCommand::formatSelection(startOfSelection, endOfSelection);
     else
         outdentRegion(startOfSelection, endOfSelection);
 }
 
 void IndentOutdentCommand::formatRange(const Position& start, const Position& end, const Position&, RefPtrWillBeRawPtr<HTMLElement>& blockquoteForNextIndent)
 {
     if (tryIndentingAsListItem(start, end))
         blockquoteForNextIndent = nullptr;
     else
         indentIntoBlockquote(start, end, blockquoteForNextIndent);
 }
 
 }