Introduce isHTMLTableElement and toHTMLTableElement

Source/core/html/HTMLTableRowsCollection.cpp

 /*
  * Copyright (C) 2008, 2011, 2012 Apple 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 136 matching lines @@
 
     return 0;
 }
 
 // Must call get() on the table in case that argument is compiled before dereferencing the
 // table to get at the collection cache. Order of argument evaluation is undefined and can
 // differ between compilers.
 HTMLTableRowsCollection::HTMLTableRowsCollection(Node* table)
     : HTMLCollection(table, TableRows, OverridesItemAfter)
 {
-    ASSERT(table->hasTagName(tableTag));
+    ASSERT(isHTMLTableElement(table));
 }
 
 PassRefPtr<HTMLTableRowsCollection> HTMLTableRowsCollection::create(Node* table, CollectionType)
 {
     return adoptRef(new HTMLTableRowsCollection(table));
 }
 
 Element* HTMLTableRowsCollection::virtualItemAfter(unsigned& offsetInArray, Element* previous) const
 {
     ASSERT_UNUSED(offsetInArray, !offsetInArray);
-    return rowAfter(static_cast<HTMLTableElement*>(ownerNode()), toHTMLTableRowElement(previous));
+    return rowAfter(toHTMLTableElement(ownerNode()), toHTMLTableRowElement(previous));
 }
 
 }