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

Source/core/editing/InputMethodController.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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 252 matching lines @@
 
     m_compositionNode = nullptr;
     m_customCompositionUnderlines.clear();
 
     if (text.isEmpty())
         return;
     ASSERT(frame().document());
     TypingCommand::insertText(*frame().document(), text, TypingCommand::SelectInsertedText | TypingCommand::PreventSpellChecking, TypingCommand::TextCompositionUpdate);
 
     // Find out what node has the composition now.
-    Position base = frame().selection().base().downstream();
+    Position base = mostForwardCaretPosition(frame().selection().base());
     Node* baseNode = base.anchorNode();
     if (!baseNode || !baseNode->isTextNode())
         return;
 
     Position extent = frame().selection().extent();
     Node* extentNode = extent.anchorNode();
     if (baseNode != extentNode)
         return;
 
     unsigned extentOffset = extent.computeOffsetInContainerNode();
@@ skipping 14 matching lines @@
 
     unsigned start = std::min(baseOffset + selectionStart, extentOffset);
     unsigned end = std::min(std::max(start, baseOffset + selectionEnd), extentOffset);
     RefPtrWillBeRawPtr<Range> selectedRange = Range::create(baseNode->document(), baseNode, start, baseNode, end);
     frame().selection().setSelectedRange(selectedRange.get(), TextAffinity::Downstream, FrameSelection::NonDirectional, NotUserTriggered);
 }
 
 void InputMethodController::setCompositionFromExistingText(const Vector<CompositionUnderline>& underlines, unsigned compositionStart, unsigned compositionEnd)
 {
     Element* editable = frame().selection().rootEditableElement();
-    Position base = frame().selection().base().downstream();
+    Position base = mostForwardCaretPosition(frame().selection().base());
     Node* baseNode = base.anchorNode();
     if (baseNode && editable->firstChild() == baseNode && editable->lastChild() == baseNode && baseNode->isTextNode()) {
         m_compositionNode = nullptr;
         m_customCompositionUnderlines.clear();
 
         if (!base.isOffsetInAnchor())
             return;
         if (baseNode != frame().selection().extent().anchorNode())
             return;
 
@@ skipping 103 matching lines @@
     TypingCommand::deleteSelection(*frame().document());
 }
 
 DEFINE_TRACE(InputMethodController)
 {
     visitor->trace(m_frame);
     visitor->trace(m_compositionNode);
 }
 
 } // namespace blink