Introduce isHTMLTableElement and toHTMLTableElement

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 41 matching lines @@
 {
     return adoptRef(new HTMLTableRowElement(tagName, document));
 }
 
 int HTMLTableRowElement::rowIndex() const
 {
     ContainerNode* table = parentNode();
     if (!table)
         return -1;
     table = table->parentNode();
-    if (!table || !table->hasTagName(tableTag))
+    if (!table || !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 = static_cast<HTMLTableElement*>(table)->tHead()) {
+    if (HTMLTableSectionElement* head = toHTMLTableElement(table)->tHead()) {
         for (Node *row = head->firstChild(); row; row = row->nextSibling()) {
             if (row == this)
                 return rIndex;
             if (row->hasTagName(trTag))
                 ++rIndex;
         }
     }
-    
+
     for (Node *node = table->firstChild(); node; node = node->nextSibling()) {
         if (node->hasTagName(tbodyTag)) {
             HTMLTableSectionElement* section = static_cast<HTMLTableSectionElement*>(node);
             for (Node* row = section->firstChild(); row; row = row->nextSibling()) {
                 if (row == this)
                     return rIndex;
                 if (row->hasTagName(trTag))
                     ++rIndex;
             }
         }
     }
 
-    if (HTMLTableSectionElement* foot = static_cast<HTMLTableElement*>(table)->tFoot()) {
+    if (HTMLTableSectionElement* foot = toHTMLTableElement(table)->tFoot()) {
         for (Node *row = foot->firstChild(); row; row = row->nextSibling()) {
             if (row == this)
                 return rIndex;
             if (row->hasTagName(trTag))
                 ++rIndex;
         }
     }
 
     // We get here for rows that are in <thead> or <tfoot> sections other than the main header and footer.
     return -1;
@@ skipping 54 matching lines @@
 {
     return ensureCachedHTMLCollection(TRCells);
 }
 
 void HTMLTableRowElement::setCells(HTMLCollection*, ExceptionCode& ec)
 {
     ec = NoModificationAllowedError;
 }
 
 }