Have the form control element directly handle validation message updating.

Source/core/html/FormAssociatedElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 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 19 matching lines @@
 
 namespace WebCore {
 
 class ContainerNode;
 class Document;
 class FormAttributeTargetObserver;
 class FormDataList;
 class HTMLElement;
 class HTMLFormElement;
 class Node;
-class ValidationMessage;
 class ValidityState;
 class VisibleSelection;
 
 class FormAssociatedElement : public WillBeGarbageCollectedMixin {
 public:
     virtual ~FormAssociatedElement();
 
 #if !ENABLE(OILPAN)
     void ref() { refFormAssociatedElement(); }
     void deref() { derefFormAssociatedElement(); }
@@ skipping 84 matching lines @@
 };
 
 HTMLElement* toHTMLElement(FormAssociatedElement*);
 HTMLElement& toHTMLElement(FormAssociatedElement&);
 const HTMLElement* toHTMLElement(const FormAssociatedElement*);
 const HTMLElement& toHTMLElement(const FormAssociatedElement&);
 
 } // namespace
 
 #endif // FormAssociatedElement_h