Introduce nextPositionOf() for VisiblePosition

Source/core/editing/Editor.cpp

Index: Source/core/editing/Editor.cpp
diff --git a/Source/core/editing/Editor.cpp b/Source/core/editing/Editor.cpp
index ce4f60ccd5a76de27a08b38dc3e002e3462f8eb2..169097fd7610c3df53302a719773719beb9c1260 100644
--- a/Source/core/editing/Editor.cpp
+++ b/Source/core/editing/Editor.cpp
@@ -1023,7 +1023,7 @@ void Editor::transpose()
 
     // Make a selection that goes back one character and forward two characters.
     VisiblePosition caret = selection.visibleStart();
-    VisiblePosition next = isEndOfParagraph(caret) ? caret : caret.next();
+    VisiblePosition next = isEndOfParagraph(caret) ? caret : nextPositionOf(caret);
     VisiblePosition previous = previousPositionOf(next);
     if (next.deepEquivalent() == previous.deepEquivalent())
         return;