Make WebNode::to<Type>() (and toConst) casts contain type asserts.

third_party/WebKit/public/web/WebLabelElement.h

 /*
  * Copyright (C) 2010 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 24 matching lines @@
 
 #if BLINK_IMPLEMENTATION
 namespace WTF { template <typename T> class PassRefPtr; }
 #endif
 
 namespace blink {
 
 class HTMLLabelElement;
 
 // Provides readonly access to some properties of a DOM label element node.
-class WebLabelElement : public WebElement {
+class WebLabelElement final : public WebElement {
 public:
     WebLabelElement() : WebElement() { }
     WebLabelElement(const WebLabelElement& element) : WebElement(element) { }
 
     WebLabelElement& operator=(const WebLabelElement& element)
     {
         WebElement::assign(element);
         return *this;
     }
 
     void assign(const WebLabelElement& element) { WebElement::assign(element); }
 
     BLINK_EXPORT WebElement correspondingControl();
 
 #if BLINK_IMPLEMENTATION
     WebLabelElement(const PassRefPtrWillBeRawPtr<HTMLLabelElement>&);
     WebLabelElement& operator=(const PassRefPtrWillBeRawPtr<HTMLLabelElement>&);
     operator PassRefPtrWillBeRawPtr<HTMLLabelElement>() const;
 #endif
 };
 
+DECLARE_WEB_NODE_TYPE_CASTS(WebLabelElement);
+
 } // namespace blink
 
 #endif