Fix build following r198658.

Source/core/editing/iterators/CharacterIterator.cpp

Index: Source/core/editing/iterators/CharacterIterator.cpp
diff --git a/Source/core/editing/iterators/CharacterIterator.cpp b/Source/core/editing/iterators/CharacterIterator.cpp
index 8d45d01290a21287bc3ad34500f3b0e0861a3af7..3ef1fc549c581c263848a934067a447ccc01176b 100644
--- a/Source/core/editing/iterators/CharacterIterator.cpp
+++ b/Source/core/editing/iterators/CharacterIterator.cpp
@@ -115,7 +115,7 @@ EphemeralRangeTemplate<Strategy> CharacterIteratorAlgorithm<Strategy>::range() c
     PositionAlgorithm<Strategy> startPosition = range.startPosition().parentAnchoredEquivalent();
     PositionAlgorithm<Strategy> endPosition = range.endPosition().parentAnchoredEquivalent();
     Node* node = startPosition.containerNode();
-    ASSERT(node == endPosition.containerNode());
+    ASSERT_UNUSED(endPosition, node == endPosition.containerNode());
     int offset = startPosition.offsetInContainerNode() + m_runOffset;
     return EphemeralRangeTemplate<Strategy>(PositionAlgorithm<Strategy>(node, offset), PositionAlgorithm<Strategy>(node, offset + 1));
 }