Do not traverse nodes not having a layout object while searching editable visible position.

Source/core/editing/htmlediting.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007 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 316 matching lines @@
     if (enclosingCell)
         return enclosingCell;
 
     return editableRootForPosition(p);
 }
 
 template <typename Strategy>
 PositionAlgorithm<Strategy> nextCandidateAlgorithm(const PositionAlgorithm<Strategy>& position)
 {
     PositionIteratorAlgorithm<Strategy> p(position);
+
+    p.increment();
     while (!p.atEnd()) {
-        p.increment();
         PositionAlgorithm<Strategy> candidate = p.computePosition();
         if (candidate.isCandidate())
             return candidate;
+
+        p.increment();
     }
+
     return PositionAlgorithm<Strategy>();
 }
 
 Position nextCandidate(const Position& position)
 {
     return nextCandidateAlgorithm<EditingStrategy>(position);
 }
 
 PositionInComposedTree nextCandidate(const PositionInComposedTree& position)
 {
     return nextCandidateAlgorithm<EditingInComposedTreeStrategy>(position);
 }
 
 // |nextVisuallyDistinctCandidate| is similar to |nextCandidate| except
 // for returning position which |downstream()| not equal to initial position's
 // |downstream()|.
 Position nextVisuallyDistinctCandidate(const Position& position)
 {
     if (position.isNull())
-        return position;
+        return Position();
+
     PositionIterator p(position);
     Position downstreamStart = position.downstream();
+
+    p.increment();
     while (!p.atEnd()) {
-        p.increment();
         Position candidate = p.computePosition();
         if (candidate.isCandidate() && candidate.downstream() != downstreamStart)
             return candidate;
+
+        p.increment();
     }
+
     return Position();
 }
 
 template <typename Strategy>
 PositionAlgorithm<Strategy> previousCandidateAlgorithm(const PositionAlgorithm<Strategy>& position)
 {
     PositionIteratorAlgorithm<Strategy> p(position);
+
+    p.decrement();
     while (!p.atStart()) {
-        p.decrement();
         PositionAlgorithm<Strategy> candidate = p.computePosition();
         if (candidate.isCandidate())
             return candidate;
+
+        p.decrement();
     }
+
     return PositionAlgorithm<Strategy>();
 }
 
 Position previousCandidate(const Position& position)
 {
     return previousCandidateAlgorithm<EditingStrategy>(position);
 }
 
 PositionInComposedTree previousCandidate(const PositionInComposedTree& position)
 {
     return previousCandidateAlgorithm<EditingInComposedTreeStrategy>(position);
 }
 
 // |previousVisuallyDistinctCandidate| is similar to |previousCandidate| except
 // for returning position which |downstream()| not equal to initial position's
 // |downstream()|.
 template <typename Strategy>
 PositionAlgorithm<Strategy> previousVisuallyDistinctCandidateAlgorithm(const PositionAlgorithm<Strategy>& position)
 {
     if (position.isNull())
-        return position;
+        return PositionAlgorithm<Strategy>();
+
     PositionIteratorAlgorithm<Strategy> p(position);
     PositionAlgorithm<Strategy> downstreamStart = position.downstream();
+
+    p.decrement();
     while (!p.atStart()) {
-        p.decrement();
         PositionAlgorithm<Strategy> candidate = p.computePosition();
         if (candidate.isCandidate() && candidate.downstream() != downstreamStart)
             return candidate;
+
+        p.decrement();
     }
+
     return PositionAlgorithm<Strategy>();
 }
 
 Position previousVisuallyDistinctCandidate(const Position& position)
 {
     return previousVisuallyDistinctCandidateAlgorithm<EditingStrategy>(position);
 }
 
 PositionInComposedTree previousVisuallyDistinctCandidate(const PositionInComposedTree& position)
 {
@@ skipping 991 matching lines @@
     // if the selection starts just before a paragraph break, skip over it
     if (isEndOfParagraph(visiblePosition))
         return visiblePosition.next().deepEquivalent().downstream();
 
     // otherwise, make sure to be at the start of the first selected node,
     // instead of possibly at the end of the last node before the selection
     return visiblePosition.deepEquivalent().downstream();
 }
 
 } // namespace blink