Get rid of a redundant argument DOWNSTREAM from VisiblePosition constructor call sites

Source/core/editing/commands/ReplaceSelectionCommand.cpp

 /*
  * Copyright (C) 2005, 2006, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009, 2010, 2011 Google Inc. 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
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 1014 matching lines @@
     // If the downstream node has been removed there's no point in continuing.
     if (!insertionPos.downstream().anchorNode())
         return;
 
     // NOTE: This would be an incorrect usage of downstream() if downstream() were changed to mean the last position after
     // p that maps to the same visible position as p (since in the case where a br is at the end of a block and collapsed
     // away, there are positions after the br which map to the same visible position as [br, 0]).
     HTMLBRElement* endBR = isHTMLBRElement(*insertionPos.downstream().anchorNode()) ? toHTMLBRElement(insertionPos.downstream().anchorNode()) : 0;
     VisiblePosition originalVisPosBeforeEndBR;
     if (endBR)
-        originalVisPosBeforeEndBR = VisiblePosition(positionBeforeNode(endBR), DOWNSTREAM).previous();
+        originalVisPosBeforeEndBR = VisiblePosition(positionBeforeNode(endBR)).previous();
 
     RefPtrWillBeRawPtr<Element> enclosingBlockOfInsertionPos = enclosingBlock(insertionPos.anchorNode());
 
     // Adjust insertionPos to prevent nesting.
     // If the start was in a Mail blockquote, we will have already handled adjusting insertionPos above.
     if (m_preventNesting && enclosingBlockOfInsertionPos && !isTableCell(enclosingBlockOfInsertionPos.get()) && !startIsInsideMailBlockquote) {
         ASSERT(enclosingBlockOfInsertionPos != currentRoot);
         VisiblePosition visibleInsertionPos(insertionPos);
         if (isEndOfBlock(visibleInsertionPos) && !(isStartOfBlock(visibleInsertionPos) && fragment.hasInterchangeNewlineAtEnd()))
             insertionPos = positionInParentAfterNode(*enclosingBlockOfInsertionPos);
@@ skipping 503 matching lines @@
 DEFINE_TRACE(ReplaceSelectionCommand)
 {
     visitor->trace(m_startOfInsertedContent);
     visitor->trace(m_endOfInsertedContent);
     visitor->trace(m_insertionStyle);
     visitor->trace(m_documentFragment);
     CompositeEditCommand::trace(visitor);
 }
 
 } // namespace blink