Introduce toHTMLInputElement(Node*), and use it.

Source/core/html/RadioInputType.cpp

Index: Source/core/html/RadioInputType.cpp
diff --git a/Source/core/html/RadioInputType.cpp b/Source/core/html/RadioInputType.cpp
index 8485762efb974cf711db61a3c3dd460b123dff83..d228a9714e02c905bfa2251990e49f943968e9c6 100644
--- a/Source/core/html/RadioInputType.cpp
+++ b/Source/core/html/RadioInputType.cpp
@@ -90,7 +90,7 @@ void RadioInputType::handleKeydownEvent(KeyboardEvent* event)
         // Look for more radio buttons.
         if (!node->hasTagName(inputTag))
             continue;
-        HTMLInputElement* inputElement = static_cast<HTMLInputElement*>(node);
+        HTMLInputElement* inputElement = toHTMLInputElement(node);
         if (inputElement->form() != element()->form())
             break;
         if (inputElement->isRadioButton() && inputElement->name() == element()->name() && inputElement->isFocusable()) {
@@ -127,7 +127,7 @@ bool RadioInputType::isKeyboardFocusable(KeyboardEvent* event) const
     // skip any other elements in the group.
     Node* currentFocusedNode = element()->document()->focusedNode();
     if (currentFocusedNode && currentFocusedNode->hasTagName(inputTag)) {
-        HTMLInputElement* focusedInput = static_cast<HTMLInputElement*>(currentFocusedNode);
+        HTMLInputElement* focusedInput = toHTMLInputElement(currentFocusedNode);
         if (focusedInput->isRadioButton() && focusedInput->form() == element()->form() && focusedInput->name() == element()->name())
             return false;
     }