Simplify watched selector handling and remove remnants of user stylesheets

Source/core/css/CSSComputedStyleDeclaration.cpp

 /*
  * Copyright (C) 2004 Zack Rusin <zack@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2011 Sencha, Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
@@ skipping 2672 matching lines @@
         case CSSPropertyMargin:
             return valuesForSidesShorthand(marginShorthand());
         case CSSPropertyOutline:
             return valuesForShorthandProperty(outlineShorthand());
         case CSSPropertyPadding:
             return valuesForSidesShorthand(paddingShorthand());
         /* Individual properties not part of the spec */
         case CSSPropertyBackgroundRepeatX:
         case CSSPropertyBackgroundRepeatY:
             break;
-        case CSSPropertyInternalCallback:
-            // This property is hidden from the web.
-            return nullptr;
 
         /* Unimplemented CSS 3 properties (including CSS3 shorthand properties) */
         case CSSPropertyWebkitTextEmphasis:
             break;
 
         /* Directional properties are resolved by resolveDirectionAwareProperty() before the switch. */
         case CSSPropertyWebkitBorderEnd:
         case CSSPropertyWebkitBorderEndColor:
         case CSSPropertyWebkitBorderEndStyle:
         case CSSPropertyWebkitBorderEndWidth:
@@ skipping 306 matching lines @@
     return list.release();
 }
 
 void CSSComputedStyleDeclaration::trace(Visitor* visitor)
 {
     visitor->trace(m_node);
     CSSStyleDeclaration::trace(visitor);
 }
 
 } // namespace blink