Update is-valid flag upon resetting input elements.

Source/core/html/HTMLInputElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2007 Samuel Weinig (sam@webkit.org)
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2012 Samsung Electronics. All rights reserved.
@@ skipping 822 matching lines @@
     return m_inputType->isFormDataAppendable() && m_inputType->appendFormData(encoding, multipart);
 }
 
 String HTMLInputElement::resultForDialogSubmit()
 {
     return m_inputType->resultForDialogSubmit();
 }
 
 void HTMLInputElement::resetImpl()
 {
-    if (m_inputType->storesValueSeparateFromAttribute())
+    if (m_inputType->storesValueSeparateFromAttribute()) {
         setValue(String());
+        setNeedsValidityCheck();
+    }
 
     setChecked(hasAttribute(checkedAttr));
     m_reflectsCheckedAttribute = true;
 }
 
 bool HTMLInputElement::isTextField() const
 {
     return m_inputType->isTextField();
 }
 
@@ skipping 1009 matching lines @@
 }
 
 #if ENABLE(INPUT_MULTIPLE_FIELDS_UI)
 PassRefPtr<RenderStyle> HTMLInputElement::customStyleForRenderer()
 {
     return m_inputTypeView->customStyleForRenderer(originalStyleForRenderer());
 }
 #endif
 
 } // namespace