Get rid of redundant member function PositionAlgorithm<Strategy>::{upstream,downstream}

Source/core/editing/commands/ApplyBlockElementCommand.cpp

Index: Source/core/editing/commands/ApplyBlockElementCommand.cpp
diff --git a/Source/core/editing/commands/ApplyBlockElementCommand.cpp b/Source/core/editing/commands/ApplyBlockElementCommand.cpp
index f5f006b6606ef06abfcf7e0c40d3c9ffc00a8b34..4ecb424767bd1789f12e366d82967d0fa8036764 100644
--- a/Source/core/editing/commands/ApplyBlockElementCommand.cpp
+++ b/Source/core/editing/commands/ApplyBlockElementCommand.cpp
@@ -110,7 +110,7 @@ void ApplyBlockElementCommand::formatSelection(const VisiblePosition& startOfSel
 {
     // Special case empty unsplittable elements because there's nothing to split
     // and there's nothing to move.
-    Position start = startOfSelection.deepEquivalent().downstream();
+    Position start = mostForwardCaretPosition(startOfSelection.deepEquivalent());
     if (isAtUnsplittableElement(start)) {
         RefPtrWillBeRawPtr<HTMLElement> blockquote = createBlockElement();
         insertNodeAt(blockquote, start);