Use new is*Element() helper functions in DOM code

Source/core/dom/shadow/ShadowRootRareData.h

Index: Source/core/dom/shadow/ShadowRootRareData.h
diff --git a/Source/core/dom/shadow/ShadowRootRareData.h b/Source/core/dom/shadow/ShadowRootRareData.h
index 4ec22d5a34195dfbd8f6a45c34a4c9d51cecd944..051579a00b2a69b19aac026eec3738d3f6f7db3a 100644
--- a/Source/core/dom/shadow/ShadowRootRareData.h
+++ b/Source/core/dom/shadow/ShadowRootRareData.h
@@ -106,9 +106,10 @@ private:
 
 inline void ShadowRootRareData::didAddInsertionPoint(InsertionPoint* point)
 {
-    if (point->hasTagName(HTMLNames::shadowTag))
+    ASSERT(point);
+    if (isHTMLShadowElement(*point))
         ++m_descendantShadowElementCount;
-    else if (point->hasTagName(HTMLNames::contentTag))
+    else if (isHTMLContentElement(*point))
         ++m_descendantContentElementCount;
     else
         ASSERT_NOT_REACHED();
@@ -116,9 +117,10 @@ inline void ShadowRootRareData::didAddInsertionPoint(InsertionPoint* point)
 
 inline void ShadowRootRareData::didRemoveInsertionPoint(InsertionPoint* point)
 {
-    if (point->hasTagName(HTMLNames::shadowTag))
+    ASSERT(point);
+    if (isHTMLShadowElement(*point))
         --m_descendantShadowElementCount;
-    else if (point->hasTagName(HTMLNames::contentTag))
+    else if (isHTMLContentElement(*point))
         --m_descendantContentElementCount;
     else
         ASSERT_NOT_REACHED();