Popup open and hide using Alt+KeyDown

Source/core/rendering/RenderTheme.h

 /*
  * This file is part of the theme implementation for form controls in WebCore.
  *
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Computer, Inc.
  *
  * 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 170 matching lines @@
     virtual int sliderTickOffsetFromTrackCenter() const = 0;
     void paintSliderTicks(RenderObject*, const PaintInfo&, const IntRect&);
 
     virtual bool shouldShowPlaceholderWhenFocused() const { return false; }
     virtual bool shouldHaveSpinButton(HTMLInputElement*) const;
 
     // Functions for <select> elements.
     virtual bool delegatesMenuListRendering() const { return false; }
     virtual bool popsMenuByArrowKeys() const { return false; }
     virtual bool popsMenuBySpaceOrReturn() const { return false; }
+    virtual bool shouldOpenDropDownWithAltDownUpOrF4Key() const { return false; }
 
     virtual String fileListNameForWidth(Locale&, const FileList*, const Font&, int width) const;
 
     virtual bool shouldOpenPickerWithF4Key() const;
 
     virtual bool supportsSelectionForegroundColors() const { return true; }
 
 protected:
     // The platform selection color.
     virtual Color platformActiveSelectionBackgroundColor() const;
@@ skipping 106 matching lines @@
     static const RGBA32 defaultCompositionBackgroundColor = 0xFFFFDD55;
 
 #if USE(NEW_THEME)
     Theme* m_platformTheme; // The platform-specific theme.
 #endif
 };
 
 } // namespace WebCore
 
 #endif // RenderTheme_h