Use new is*Element() helper functions further more in HTML code

Source/core/html/HTMLOptGroupElement.cpp

Index: Source/core/html/HTMLOptGroupElement.cpp
diff --git a/Source/core/html/HTMLOptGroupElement.cpp b/Source/core/html/HTMLOptGroupElement.cpp
index e45aacc493c0814d08b2ae59b2ee0deb9d33eea0..314e220d088510271d3c705f7d8c1ff1d8a13450 100644
--- a/Source/core/html/HTMLOptGroupElement.cpp
+++ b/Source/core/html/HTMLOptGroupElement.cpp
@@ -76,7 +76,7 @@ void HTMLOptGroupElement::parseAttribute(const QualifiedName& name, const Atomic
 void HTMLOptGroupElement::recalcSelectOptions()
 {
     ContainerNode* select = parentNode();
-    while (select && !select->hasTagName(selectTag))
+    while (select && !isHTMLSelectElement(*select))
         select = select->parentNode();
     if (select)
         toHTMLSelectElement(select)->setRecalcListItems();
@@ -128,7 +128,7 @@ String HTMLOptGroupElement::groupLabelText() const
 HTMLSelectElement* HTMLOptGroupElement::ownerSelectElement() const
 {
     ContainerNode* select = parentNode();
-    while (select && !select->hasTagName(selectTag))
+    while (select && !isHTMLSelectElement(*select))
         select = select->parentNode();
 
     if (!select)