Introduce isHTMLLabelElement and toHTMLLabelElement

Source/core/html/LabelsNodeList.cpp

Index: Source/core/html/LabelsNodeList.cpp
diff --git a/Source/core/html/LabelsNodeList.cpp b/Source/core/html/LabelsNodeList.cpp
index f925e9fd57b29ee7760c7b599c00412b65575103..a822c47ae6f514651cb90a8ca2357368b88080c2 100644
--- a/Source/core/html/LabelsNodeList.cpp
+++ b/Source/core/html/LabelsNodeList.cpp
@@ -41,11 +41,11 @@ LabelsNodeList::LabelsNodeList(Node* forNode)
 LabelsNodeList::~LabelsNodeList()
 {
     ownerNode()->nodeLists()->removeCacheWithAtomicName(this, LabelsNodeListType, starAtom);
-} 
-    
+}
+
 bool LabelsNodeList::nodeMatches(Element* testNode) const
 {
-    return testNode->hasTagName(labelTag) && static_cast<HTMLLabelElement*>(testNode)->control() == ownerNode();
+    return isHTMLLabelElement(testNode) && toHTMLLabelElement(testNode)->control() == ownerNode();
 }
 
 } // namespace WebCore