Oilpan: fix MSVC compilation after r180556.

Source/core/css/CSSRule.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * (C) 2002-2003 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2002, 2005, 2006, 2007, 2012 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 11 matching lines @@
 #include "config.h"
 #include "core/css/CSSRule.h"
 
 #include "core/css/CSSStyleSheet.h"
 #include "core/css/StyleRule.h"
 #include "core/css/StyleSheetContents.h"
 #include "platform/NotImplemented.h"
 
 namespace blink {
 
-struct SameSizeAsCSSRule : public RefCountedWillBeGarbageCollectedFinalized<SameSizeAsCSSRule> {
+struct SameSizeAsCSSRule : public RefCountedWillBeGarbageCollectedFinalized<SameSizeAsCSSRule>, public ScriptWrappableBase {
     virtual ~SameSizeAsCSSRule();
     unsigned char bitfields;
     void* pointerUnion;
 };
 
 COMPILE_ASSERT(sizeof(CSSRule) == sizeof(SameSizeAsCSSRule), CSSRule_should_stay_small);
 
 COMPILE_ASSERT(StyleRuleBase::Viewport == static_cast<StyleRuleBase::Type>(CSSRule::VIEWPORT_RULE), enums_should_match);
 
 void CSSRule::setCSSText(const String&)
@@ skipping 14 matching lines @@
     // pre-oilpan world, where the parent link is mysteriously zeroed under
     // some circumstances.
     if (m_parentIsRule)
         visitor->trace(m_parentRule);
     else
         visitor->trace(m_parentStyleSheet);
 #endif
 }
 
 } // namespace blink