<label> should support form association by parser

Source/core/html/HTMLObjectElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 109 matching lines @@
 
 // Intentionally left unimplemented, template specialization needs to be provided for specific
 // return types.
 template<typename T> inline const T& toElement(const FormAssociatedElement&);
 template<typename T> inline const T* toElement(const FormAssociatedElement*);
 
 // Make toHTMLObjectElement() accept a FormAssociatedElement as input instead of a Node.
 template<> inline const HTMLObjectElement* toElement<HTMLObjectElement>(const FormAssociatedElement* element)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!element || !element->isFormControlElement());
+    ASSERT_WITH_SECURITY_IMPLICATION(!element || !element->isLabelElement());
     const HTMLObjectElement* objectElement = static_cast<const HTMLObjectElement*>(element);
     // We need to assert after the cast because FormAssociatedElement doesn't
     // have hasTagName.
     ASSERT_WITH_SECURITY_IMPLICATION(!objectElement || objectElement->hasTagName(HTMLNames::objectTag));
     return objectElement;
 }
 
 template<> inline const HTMLObjectElement& toElement<HTMLObjectElement>(const FormAssociatedElement& element)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!element.isFormControlElement());
+    ASSERT_WITH_SECURITY_IMPLICATION(!element.isLabelElement());
     const HTMLObjectElement& objectElement = static_cast<const HTMLObjectElement&>(element);
     // We need to assert after the cast because FormAssociatedElement doesn't
     // have hasTagName.
     ASSERT_WITH_SECURITY_IMPLICATION(objectElement.hasTagName(HTMLNames::objectTag));
     return objectElement;
 }
 
 } // namespace blink
 
 #endif // HTMLObjectElement_h