Refactoring: toHTMLElement(const Node*) added but never used. Using it.

Source/core/editing/MarkupAccumulator.cpp

Index: Source/core/editing/MarkupAccumulator.cpp
diff --git a/Source/core/editing/MarkupAccumulator.cpp b/Source/core/editing/MarkupAccumulator.cpp
index e619430fa3c8aca7296fe6df2a86584503543494..dadc6a4ec7c51e2c9967da466ea72e0d7445906b 100644
--- a/Source/core/editing/MarkupAccumulator.cpp
+++ b/Source/core/editing/MarkupAccumulator.cpp
@@ -538,7 +538,7 @@ bool MarkupAccumulator::elementCannotHaveEndTag(const Node* node)
     // ieForbidsInsertHTML is used to disallow setting innerHTML/outerHTML
     // or createContextualFragment.  It does not necessarily align with
     // which elements should be serialized w/o end tags.
-    return static_cast<const HTMLElement*>(node)->ieForbidsInsertHTML();
+    return toHTMLElement(node)->ieForbidsInsertHTML();
 }
 
 void MarkupAccumulator::appendEndMarkup(StringBuilder& result, const Node* node)