Remove unused MarginBoxType

Source/core/css/CSSSelector.h

 /*
  * Copyright (C) 1999-2003 Lars Knoll (knoll@kde.org)
  *               1999 Waldo Bastian (bastian@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc. 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 185 matching lines @@
         PseudoPastCue,
         PseudoUnresolved,
         PseudoContent,
         PseudoHost,
         PseudoHostContext,
         PseudoShadow,
         PseudoSpatialNavigationFocus,
         PseudoListBox
     };
 
-    enum MarginBoxType {
-        TopLeftCornerMarginBox,
-        TopLeftMarginBox,
-        TopCenterMarginBox,
-        TopRightMarginBox,
-        TopRightCornerMarginBox,
-        BottomLeftCornerMarginBox,
-        BottomLeftMarginBox,
-        BottomCenterMarginBox,
-        BottomRightMarginBox,
-        BottomRightCornerMarginBox,
-        LeftTopMarginBox,
-        LeftMiddleMarginBox,
-        LeftBottomMarginBox,
-        RightTopMarginBox,
-        RightMiddleMarginBox,
-        RightBottomMarginBox,
-    };
-
     enum AttributeMatchType {
         CaseSensitive,
         CaseInsensitive,
     };
 
     PseudoType pseudoType() const { return static_cast<PseudoType>(m_pseudoType); }
     void updatePseudoType(const AtomicString&, bool hasArguments);
 
     static PseudoType parsePseudoType(const AtomicString&, bool hasArguments);
     static PseudoId pseudoId(PseudoType);
@@ skipping 244 matching lines @@
     if (m_hasRareData)
         return m_data.m_rareData->m_value;
     // AtomicString is really just a StringImpl* so the cast below is safe.
     // FIXME: Perhaps call sites could be changed to accept StringImpl?
     return *reinterpret_cast<const AtomicString*>(&m_data.m_value);
 }
 
 } // namespace blink
 
 #endif // CSSSelector_h