Introduce composed tree version of leftPositionOf()

Source/core/editing/VisiblePosition.h

 /*
  * Copyright (C) 2004, 2008 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 101 matching lines @@
 
 extern template class CORE_EXTERN_TEMPLATE_EXPORT VisiblePositionTemplate<EditingStrategy>;
 extern template class CORE_EXTERN_TEMPLATE_EXPORT VisiblePositionTemplate<EditingInComposedTreeStrategy>;
 
 using VisiblePosition = VisiblePositionTemplate<EditingStrategy>;
 using VisiblePositionInComposedTree = VisiblePositionTemplate<EditingInComposedTreeStrategy>;
 
 CORE_EXPORT VisiblePosition createVisiblePosition(const Position&, TextAffinity = VP_DEFAULT_AFFINITY);
 CORE_EXPORT VisiblePosition createVisiblePosition(const PositionWithAffinity&);
 CORE_EXPORT VisiblePositionInComposedTree createVisiblePosition(const PositionInComposedTree&, TextAffinity = VP_DEFAULT_AFFINITY);
+CORE_EXPORT VisiblePositionInComposedTree createVisiblePosition(const PositionInComposedTreeWithAffinity&);
 
 // TODO(yosin) Once we have composed tree version of VisibleUnits, we should not
 // use |createVisiblePositionInDOMTree()|.
 VisiblePosition createVisiblePositionInDOMTree(const Position&, TextAffinity = VP_DEFAULT_AFFINITY);
 VisiblePosition createVisiblePositionInDOMTree(const PositionInComposedTree&, TextAffinity = VP_DEFAULT_AFFINITY);
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showTree(const blink::VisiblePosition*);
 void showTree(const blink::VisiblePosition&);
 #endif
 
 #endif // VisiblePosition_h