Introduce composed tree version of leftPositionOf()

Source/core/editing/VisiblePosition.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Portions Copyright (c) 2011 Motorola Mobility, 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 75 matching lines @@
 VisiblePosition createVisiblePosition(const PositionWithAffinity& positionWithAffinity)
 {
     return VisiblePosition::create(positionWithAffinity);
 }
 
 VisiblePositionInComposedTree createVisiblePosition(const PositionInComposedTree& position, TextAffinity affinity)
 {
     return VisiblePositionInComposedTree::create(PositionInComposedTreeWithAffinity(position, affinity));
 }
 
+VisiblePositionInComposedTree createVisiblePosition(const PositionInComposedTreeWithAffinity& positionWithAffinity)
+{
+    return VisiblePositionInComposedTree::create(positionWithAffinity);
+}
+
 VisiblePosition createVisiblePositionInDOMTree(const Position& position, TextAffinity affinity)
 {
     return createVisiblePosition(position, affinity);
 }
 
 VisiblePosition createVisiblePositionInDOMTree(const PositionInComposedTree& position, TextAffinity affinity)
 {
     const VisiblePositionInComposedTree visiblePosition = createVisiblePosition(position);
     return createVisiblePosition(toPositionInDOMTree(visiblePosition.deepEquivalent()), affinity);
 }
@@ skipping 38 matching lines @@
     else
         fprintf(stderr, "Cannot showTree for (nil) VisiblePosition.\n");
 }
 
 void showTree(const blink::VisiblePosition& vpos)
 {
     vpos.showTreeForThis();
 }
 
 #endif