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

third_party/WebKit/public/web/WebFormElement.h

 /*
  * Copyright (C) 2009 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 23 matching lines @@
 #include "../platform/WebVector.h"
 #include "WebElement.h"
 
 namespace blink {
 
 class HTMLFormElement;
 class WebFormControlElement;
 
 // A container for passing around a reference to a form element. Provides some
 // information about the form.
-class WebFormElement : public WebElement {
+class WebFormElement final : public WebElement {
 public:
     ~WebFormElement() { reset(); }
 
     WebFormElement() : WebElement() { }
     WebFormElement(const WebFormElement& element) : WebElement(element) { }
 
     WebFormElement& operator=(const WebFormElement& element)
     {
         WebElement::assign(element);
         return *this;
@@ skipping 21 matching lines @@
     };
     BLINK_EXPORT void finishRequestAutocomplete(WebFormElement::AutocompleteResult);
 
 #if BLINK_IMPLEMENTATION
     WebFormElement(const PassRefPtrWillBeRawPtr<HTMLFormElement>&);
     WebFormElement& operator=(const PassRefPtrWillBeRawPtr<HTMLFormElement>&);
     operator PassRefPtrWillBeRawPtr<HTMLFormElement>() const;
 #endif
 };
 
+DECLARE_WEB_NODE_TYPE_CASTS(WebFormElement);
+
 } // namespace blink
 
 #endif