Introduce isHTMLTableElement and toHTMLTableElement

Source/core/html/HTMLTableRowElement.cpp

Index: Source/core/html/HTMLTableRowElement.cpp
diff --git a/Source/core/html/HTMLTableRowElement.cpp b/Source/core/html/HTMLTableRowElement.cpp
index 8d37d0eb0cc43ddf796049e7ead1b6257de12e3c..79882ae1ce9f78185857686d30cc423344e1debf 100644
--- a/Source/core/html/HTMLTableRowElement.cpp
+++ b/Source/core/html/HTMLTableRowElement.cpp
@@ -59,7 +59,7 @@ int HTMLTableRowElement::rowIndex() const
     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:
@@ -69,7 +69,7 @@ int HTMLTableRowElement::rowIndex() const
 
     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;
@@ -77,7 +77,7 @@ int HTMLTableRowElement::rowIndex() const
                 ++rIndex;
         }
     }
-    
+
     for (Node *node = table->firstChild(); node; node = node->nextSibling()) {
         if (node->hasTagName(tbodyTag)) {
             HTMLTableSectionElement* section = static_cast<HTMLTableSectionElement*>(node);
@@ -90,7 +90,7 @@ int HTMLTableRowElement::rowIndex() const
         }
     }
 
-    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;