Introduce composed tree version of firstEditableVisiblePositionAfterPositionInRoot()

Source/core/editing/EditingUtilities.h

 /*
  * Copyright (C) 2004, 2006, 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 218 matching lines @@
 Position trailingWhitespacePosition(const Position&, TextAffinity, WhitespacePositionOption = NotConsiderNonCollapsibleWhitespace);
 unsigned numEnclosingMailBlockquotes(const Position&);
 void updatePositionForNodeRemoval(Position&, Node&);
 
 // -------------------------------------------------------------------------
 // VisiblePosition
 // -------------------------------------------------------------------------
 
 // Functions returning VisiblePosition
 
-VisiblePosition firstEditableVisiblePositionAfterPositionInRoot(const Position&, ContainerNode*);
+// TODO(yosin) We should rename
+// |firstEditableVisiblePositionAfterPositionInRoot()| to a better name which
+// describes what this function returns, since it returns a position before
+// specified position due by canonicalization.
+CORE_EXPORT VisiblePosition firstEditableVisiblePositionAfterPositionInRoot(const Position&, ContainerNode*);
+CORE_EXPORT VisiblePositionInComposedTree firstEditableVisiblePositionAfterPositionInRoot(const PositionInComposedTree&, ContainerNode*);
 VisiblePosition lastEditableVisiblePositionBeforePositionInRoot(const Position&, ContainerNode*);
 VisiblePosition visiblePositionBeforeNode(Node&);
 VisiblePosition visiblePositionAfterNode(Node&);
 
 bool lineBreakExistsAtVisiblePosition(const VisiblePosition&);
 
 int comparePositions(const VisiblePosition&, const VisiblePosition&);
 
 int indexForVisiblePosition(const VisiblePosition&, RefPtrWillBeRawPtr<ContainerNode>& scope);
 EphemeralRange makeRange(const VisiblePosition&, const VisiblePosition&);
@@ skipping 65 matching lines @@
     // FIXME: this is required until 6853027 is fixed and text checking can do this for us.
     return character == '\'' || character == rightSingleQuotationMarkCharacter || character == hebrewPunctuationGershayimCharacter;
 }
 
 String stringWithRebalancedWhitespace(const String&, bool startIsStartOfParagraph, bool endIsEndOfParagraph);
 const String& nonBreakingSpaceString();
 
 }
 
 #endif