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

Source/core/layout/PendingSelection.cpp

Index: Source/core/layout/PendingSelection.cpp
diff --git a/Source/core/layout/PendingSelection.cpp b/Source/core/layout/PendingSelection.cpp
index 7faf797afed4c752feb187ac758cc39fc503a129..49fc55bbf5b66d64624a0c98e2413d1e5673bbbb 100644
--- a/Source/core/layout/PendingSelection.cpp
+++ b/Source/core/layout/PendingSelection.cpp
@@ -87,7 +87,9 @@ VisibleSelection PendingSelection::calcVisibleSelectionAlgorithm() const
     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;
     }