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

Source/core/editing/serializers/StyledMarkupSerializer.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009, 2010, 2011 Google Inc. All rights reserved.
  * Copyright (C) 2011 Igalia S.L.
  * Copyright (C) 2011 Motorola Mobility. 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
@@ skipping 119 matching lines @@
     , m_shouldAnnotate(shouldAnnotate)
     , m_highestNodeToBeSerialized(highestNodeToBeSerialized)
     , m_convertBlocksToInlines(convertBlocksToInlines)
     , m_lastClosed(highestNodeToBeSerialized)
 {
 }
 
 static bool needInterchangeNewlineAfter(const VisiblePosition& v)
 {
     VisiblePosition next = v.next();
-    Node* upstreamNode = next.deepEquivalent().upstream().anchorNode();
-    Node* downstreamNode = v.deepEquivalent().downstream().anchorNode();
+    Node* upstreamNode = mostBackwardCaretPosition(next.deepEquivalent()).anchorNode();
+    Node* downstreamNode = mostForwardCaretPosition(v.deepEquivalent()).anchorNode();
     // Add an interchange newline if a paragraph break is selected and a br won't already be added to the markup to represent it.
     return isEndOfParagraph(v) && isStartOfParagraph(next) && !(isHTMLBRElement(*upstreamNode) && upstreamNode == downstreamNode);
 }
 
 static bool needInterchangeNewlineAt(const VisiblePosition& v)
 {
     // FIXME: |v.previous()| works on a DOM tree. We need to fix this to work on
     // a composed tree.
     return needInterchangeNewlineAfter(v.previous());
 }
@@ skipping 323 matching lines @@
     if (element.isHTMLElement() && shouldAnnotate())
         inlineStyle->mergeStyleFromRulesForSerialization(&toHTMLElement(element));
 
     return inlineStyle;
 }
 
 template class StyledMarkupSerializer<EditingStrategy>;
 template class StyledMarkupSerializer<EditingInComposedTreeStrategy>;
 
 } // namespace blink