Introduce isVisuallyEquivalentCandidate() as replacement of PositionAlgorithm::isCandidate()

Source/core/editing/commands/InsertTextCommand.cpp

 /*
  * Copyright (C) 2005 Apple Computer, 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 159 matching lines @@
     // Insert the character at the leftmost candidate.
     startPosition = startPosition.upstream();
 
     // It is possible for the node that contains startPosition to contain only unrendered whitespace,
     // and so deleteInsignificantText could remove it.  Save the position before the node in case that happens.
     ASSERT(startPosition.computeContainerNode());
     Position positionBeforeStartNode(positionInParentBeforeNode(*startPosition.computeContainerNode()));
     deleteInsignificantText(startPosition, startPosition.downstream());
     if (!startPosition.inDocument())
         startPosition = positionBeforeStartNode;
-    if (!startPosition.isCandidate())
+    if (!isVisuallyEquivalentCandidate(startPosition))
         startPosition = startPosition.downstream();
 
     startPosition = positionAvoidingSpecialElementBoundary(startPosition);
 
     Position endPosition;
 
     if (m_text == "\t") {
         endPosition = insertTab(startPosition);
         startPosition = endPosition.previous();
         if (placeholder.isNotNull())
@@ skipping 73 matching lines @@
                 splitTextNode(textNode, offset);
             insertNodeBefore(spanElement, textNode.release());
         }
     }
 
     // return the position following the new tab
     return lastPositionInNode(spanElement.get());
 }
 
 }