Optimize / clean up hasTagName() call sites

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 69b8673e7f2ab85335a56e88e9e1f906f9c55a74..ee12e50793c8ae2eeafab5f96e49e20ab5904795 100644
--- a/Source/core/editing/MarkupAccumulator.cpp
+++ b/Source/core/editing/MarkupAccumulator.cpp
@@ -125,9 +125,9 @@ String MarkupAccumulator::serializeNodes(Node& targetNode, EChildrenOnly childre
 
 void MarkupAccumulator::serializeNodesWithNamespaces(Node& targetNode, EChildrenOnly childrenOnly, const Namespaces* namespaces, Vector<QualifiedName>* tagNamesToSkip)
 {
-    if (tagNamesToSkip) {
+    if (tagNamesToSkip && targetNode.isElementNode()) {
         for (size_t i = 0; i < tagNamesToSkip->size(); ++i) {
-            if (targetNode.hasTagName(tagNamesToSkip->at(i)))
+            if (toElement(targetNode).hasTagName(tagNamesToSkip->at(i)))
                 return;
         }
     }