Have HTMLTableRowsCollection::item() return an HTMLTableRowElement*

Source/core/html/HTMLTableRowsCollection.h

Index: Source/core/html/HTMLTableRowsCollection.h
diff --git a/Source/core/html/HTMLTableRowsCollection.h b/Source/core/html/HTMLTableRowsCollection.h
index 739a0565d85d85de3c1f25a9ab1ab566b1901c9b..339c218f09802b5b9ce810b63f71cf3df2dbadd1 100644
--- a/Source/core/html/HTMLTableRowsCollection.h
+++ b/Source/core/html/HTMLTableRowsCollection.h
@@ -30,6 +30,7 @@
 #define HTMLTableRowsCollection_h
 
 #include "core/html/HTMLCollection.h"
+#include "core/html/HTMLTableRowElement.h"
 
 namespace blink {
 
@@ -40,6 +41,8 @@ class HTMLTableRowsCollection FINAL : public HTMLCollection {
 public:
     static PassRefPtrWillBeRawPtr<HTMLTableRowsCollection> create(ContainerNode&, CollectionType);
 
+    HTMLTableRowElement* item(unsigned offset) const { return toHTMLTableRowElement(HTMLCollection::item(offset)); }
+
     static HTMLTableRowElement* rowAfter(HTMLTableElement&, HTMLTableRowElement*);
     static HTMLTableRowElement* lastRow(HTMLTableElement&);