Fix for input/datalist failure when datalist is created outside document

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 709 matching lines @@
     } else if (name == disabledAttr) {
         HTMLTextFormControlElement::parseAttribute(name, value);
         m_inputTypeView->disabledAttributeChanged();
     } else if (name == readonlyAttr) {
         HTMLTextFormControlElement::parseAttribute(name, value);
         m_inputTypeView->readonlyAttributeChanged();
     } else if (name == listAttr) {
         m_hasNonEmptyList = !value.isEmpty();
         if (m_hasNonEmptyList) {
             resetListAttributeTargetObserver();
-            listAttributeTargetChanged();
         }
         UseCounter::count(document(), UseCounter::ListAttribute);
     } else if (name == webkitdirectoryAttr) {
         HTMLTextFormControlElement::parseAttribute(name, value);
         UseCounter::count(document(), UseCounter::PrefixedDirectoryAttribute);
     }
     else
         HTMLTextFormControlElement::parseAttribute(name, value);
     m_inputTypeView->attributeChanged();
 }
@@ skipping 792 matching lines @@
 
 void HTMLInputElement::setListAttributeTargetObserver(PassOwnPtrWillBeRawPtr<ListAttributeTargetObserver> newObserver)
 {
     if (m_listAttributeTargetObserver)
         m_listAttributeTargetObserver->unregister();
     m_listAttributeTargetObserver = newObserver;
 }
 
 void HTMLInputElement::resetListAttributeTargetObserver()
 {
+    listAttributeTargetChanged();
     if (inDocument())
         setListAttributeTargetObserver(ListAttributeTargetObserver::create(fastGetAttribute(listAttr), this));
     else
         setListAttributeTargetObserver(nullptr);
 }
 
 void HTMLInputElement::listAttributeTargetChanged()
 {
     m_inputTypeView->listAttributeTargetChanged();
 }
@@ skipping 331 matching lines @@
     return m_inputTypeView->customStyleForRenderer(originalStyleForRenderer());
 }
 #endif
 
 bool HTMLInputElement::shouldDispatchFormControlChangeEvent(String& oldValue, String& newValue)
 {
     return m_inputType->shouldDispatchFormControlChangeEvent(oldValue, newValue);
 }
 
 } // namespace