Use DEFINE_NODE_TYPE_CASTS instead of using manual toHTMLFooElement()

Source/core/html/HTMLPlugInElement.h

Index: Source/core/html/HTMLPlugInElement.h
diff --git a/Source/core/html/HTMLPlugInElement.h b/Source/core/html/HTMLPlugInElement.h
index 0647dfd3d2422d80829c2582f571d44aef7139ff..23cb385f3d4f59258bfe7e676aa64f34920e4f3e 100644
--- a/Source/core/html/HTMLPlugInElement.h
+++ b/Source/core/html/HTMLPlugInElement.h
@@ -103,20 +103,7 @@ private:
     DisplayState m_displayState;
 };
 
-inline HTMLPlugInElement* toHTMLPlugInElement(Node* node)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->isPluginElement());
-    return static_cast<HTMLPlugInElement*>(node);
-}
-
-inline const HTMLPlugInElement* toHTMLPlugInElement(const Node* node)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->isPluginElement());
-    return static_cast<const HTMLPlugInElement*>(node);
-}
-
-// This will catch anyone doing an unnecessary cast.
-void toHTMLPlugInElement(const HTMLPlugInElement*);
+DEFINE_NODE_TYPE_CASTS(HTMLPlugInElement, isPluginElement());
 
 } // namespace WebCore