Introduce {next,previous}PositionOf() as replacement of {next,previous}() member functions in Positi

Source/core/layout/PendingSelection.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 69 matching lines @@
     using PositionType = typename Strategy::PositionType;
 
     PositionType start = Strategy::selectionStart(m_selection);
     PositionType end = Strategy::selectionEnd(m_selection);
     SelectionType selectionType = VisibleSelection::selectionType(start, end);
     TextAffinity affinity = m_selection.affinity();
 
     bool paintBlockCursor = m_shouldShowBlockCursor && selectionType == SelectionType::CaretSelection && !isLogicalEndOfLine(VisiblePosition(end, affinity));
     VisibleSelection selection;
     if (enclosingTextFormControl(start.computeContainerNode())) {
-        PositionType endPosition = paintBlockCursor ? Strategy::selectionExtent(m_selection).next() : end;
+        // TODO(yosin) We should use |PositionMoveType::Character| to avoid
+        // ending paint at middle of character.
+        PositionType endPosition = paintBlockCursor ? nextPositionOf(Strategy::selectionExtent(m_selection), PositionMoveType::CodePoint) : end;
         selection.setWithoutValidation(start, endPosition);
         return selection;
     }
 
     VisiblePosition visibleStart = VisiblePosition(start, selectionType == SelectionType::RangeSelection ? TextAffinity::Downstream : affinity);
     if (paintBlockCursor) {
         VisiblePosition visibleExtent(end, affinity);
         visibleExtent = visibleExtent.next(CanSkipOverEditingBoundary);
         return VisibleSelection(visibleStart, visibleExtent);
     }
     VisiblePosition visibleEnd(end, selectionType == SelectionType::RangeSelection ? TextAffinity::Upstream : affinity);
     return VisibleSelection(visibleStart, visibleEnd);
 }
 
 VisibleSelection PendingSelection::calcVisibleSelection() const
 {
     if (RuntimeEnabledFeatures::selectionForComposedTreeEnabled())
         return calcVisibleSelectionAlgorithm<VisibleSelection::InComposedTree>();
     return calcVisibleSelectionAlgorithm<VisibleSelection::InDOMTree>();
 }
 
 DEFINE_TRACE(PendingSelection)
 {
     visitor->trace(m_selection);
 }
 
 } // namespace blink