Fix calculateCharacterSubrange() when length == 0

third_party/WebKit/Source/core/editing/iterators/CharacterIterator.cpp

Index: third_party/WebKit/Source/core/editing/iterators/CharacterIterator.cpp
diff --git a/third_party/WebKit/Source/core/editing/iterators/CharacterIterator.cpp b/third_party/WebKit/Source/core/editing/iterators/CharacterIterator.cpp
index 73404bec56e04cc7316619bf03240e7864d90514..19b4b31007f8b577f060b5ca335f26f4eab7ebab 100644
--- a/third_party/WebKit/Source/core/editing/iterators/CharacterIterator.cpp
+++ b/third_party/WebKit/Source/core/editing/iterators/CharacterIterator.cpp
@@ -189,6 +189,8 @@ CharacterIteratorAlgorithm<Strategy>::calculateCharacterSubrange(int offset,
   advance(offset);
   const PositionTemplate<Strategy> startPos = startPosition();
 
+  if (!length)
+    return EphemeralRangeTemplate<Strategy>(startPos, startPos);
   if (length > 1)
     advance(length - 1);
   return EphemeralRangeTemplate<Strategy>(startPos, endPosition());