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

Source/core/html/HTMLTableRowElement.cpp

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2010 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 37 matching lines @@
 {
     return adoptRef(new HTMLTableRowElement(document));
 }
 
 int HTMLTableRowElement::rowIndex() const
 {
     ContainerNode* table = parentNode();
     if (!table)
         return -1;
     table = table->parentNode();
-    if (!table || !table->hasTagName(tableTag))
+    if (!isHTMLTableElement(table))
         return -1;
 
     // To match Firefox, the row indices work like this:
     //   Rows from the first <thead> are numbered before all <tbody> rows.
     //   Rows from the first <tfoot> are numbered after all <tbody> rows.
     //   Rows from other <thead> and <tfoot> elements don't get row indices at all.
 
     int rIndex = 0;
 
     if (HTMLTableSectionElement* head = toHTMLTableElement(table)->tHead()) {
@@ skipping 23 matching lines @@
         }
     }
 
     // We get here for rows that are in <thead> or <tfoot> sections other than the main header and footer.
     return -1;
 }
 
 int HTMLTableRowElement::sectionRowIndex() const
 {
     int rIndex = 0;
-    const Node *n = this;
+    const Node* n = this;
     do {
         n = n->previousSibling();
-        if (n && n->hasTagName(trTag))
-            rIndex++;
-    }
-    while (n);
+        if (n && isHTMLTableRowElement(*n))
+            ++rIndex;
+    } while (n);
 
     return rIndex;
 }
 
 PassRefPtr<HTMLElement> HTMLTableRowElement::insertCell(int index, ExceptionState& exceptionState)
 {
     RefPtr<HTMLCollection> children = cells();
     int numCells = children ? children->length() : 0;
     if (index < -1 || index > numCells) {
         exceptionState.throwDOMException(IndexSizeError, "The value provided (" + String::number(index) + ") is outside the range [-1, " + String::number(numCells) + "].");
@@ skipping 27 matching lines @@
         exceptionState.throwDOMException(IndexSizeError, "The value provided (" + String::number(index) + ") is outside the range [0, " + String::number(numCells) + ").");
     }
 }
 
 PassRefPtr<HTMLCollection> HTMLTableRowElement::cells()
 {
     return ensureCachedHTMLCollection(TRCells);
 }
 
 }