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

Source/core/dom/shadow/ShadowRootRareData.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 88 matching lines @@
 
     unsigned m_childrenAffectedByDirectAdjacentRules : 1;
     unsigned m_childrenAffectedByForwardPositionalRules : 1;
     unsigned m_childrenAffectedByBackwardPositionalRules : 1;
     unsigned m_childrenAffectedByFirstChildRules : 1;
     unsigned m_childrenAffectedByLastChildRules : 1;
 };
 
 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();
 }
 
 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();
 
     ASSERT(m_descendantContentElementCount >= 0);
     ASSERT(m_descendantShadowElementCount >= 0);
 }
 
 } // namespace WebCore
 
 #endif