[Attempt 2] Inform Chrome client of changes to an input's datalist.

Source/core/page/ChromeClient.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple, Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  * Copyright (C) 2012 Samsung Electronics. 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 210 matching lines @@
     virtual bool shouldDisableDesktopWorkarounds() { return false; }
 
     virtual FloatSize minimumWindowSize() const { return FloatSize(100, 100); }
 
     virtual bool isChromeClientImpl() const { return false; }
 
     virtual void didAssociateFormControls(const WillBeHeapVector<RefPtrWillBeMember<Element>>&, LocalFrame*) { }
     virtual void didChangeValueInTextField(HTMLFormControlElement&) { }
     virtual void didEndEditingOnTextField(HTMLInputElement&) { }
     virtual void handleKeyboardEventOnTextField(HTMLInputElement&, KeyboardEvent&) { }
+    virtual void textFieldDataListChanged(HTMLInputElement&) { }
 
     // Input mehtod editor related functions.
     virtual void didCancelCompositionOnSelectionChange() { }
     virtual void willSetInputMethodState() { }
     virtual void didUpdateTextOfFocusedElementByNonUserInput() { }
     virtual void showImeIfNeeded() { }
 
 protected:
     virtual ~ChromeClient() { }
 };
 
 } // namespace blink
 
 #endif // ChromeClient_h