Minimize calls to Node::nodeType() as it is virtual

Source/core/xml/XPathUtil.cpp

Index: Source/core/xml/XPathUtil.cpp
diff --git a/Source/core/xml/XPathUtil.cpp b/Source/core/xml/XPathUtil.cpp
index b36abf3de0e3240c2520e7bba9b289d2fa2e18bd..6b40d7535fb3ed1abb81af715903ada477cce9e4 100644
--- a/Source/core/xml/XPathUtil.cpp
+++ b/Source/core/xml/XPathUtil.cpp
@@ -49,7 +49,7 @@ String stringValue(Node* node)
         case Node::CDATA_SECTION_NODE:
             return node->nodeValue();
         default:
-            if (isRootDomNode(node) || node->nodeType() == Node::ELEMENT_NODE) {
+            if (isRootDomNode(node) || node->isElementNode()) {
                 StringBuilder result;
                 result.reserveCapacity(1024);