[WIP] do something :-)

Source/core/css/RuleSet.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 91 matching lines @@
     unsigned m_position : 18;
     unsigned m_specificity : 24;
     unsigned m_containsUncommonAttributeSelector : 1;
     unsigned m_linkMatchType : 2; //  CSSSelector::LinkMatchMask
     unsigned m_hasDocumentSecurityOrigin : 1;
     unsigned m_propertyWhitelistType : 2;
     // Use plain array instead of a Vector to minimize memory overhead.
     unsigned m_descendantSelectorIdentifierHashes[maximumIdentifierCount];
 };
 
-struct SameSizeAsRuleData {
-    DISALLOW_ALLOCATION();
-    void* a;
-    unsigned b;
-    unsigned c;
-    unsigned d[4];
-};
-
-static_assert(sizeof(RuleData) == sizeof(SameSizeAsRuleData), "RuleData should stay small");
-
 class CORE_EXPORT RuleSet : public NoBaseWillBeGarbageCollectedFinalized<RuleSet> {
     WTF_MAKE_NONCOPYABLE(RuleSet);
     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED(RuleSet);
 public:
     static PassOwnPtrWillBeRawPtr<RuleSet> create() { return adoptPtrWillBeNoop(new RuleSet); }
 
     void addRulesFromSheet(StyleSheetContents*, const MediaQueryEvaluator&, AddRuleFlags = RuleHasNoSpecialState);
     void addStyleRule(StyleRule*, AddRuleFlags);
     void addRule(StyleRule*, unsigned selectorIndex, AddRuleFlags);
 
@@ skipping 100 matching lines @@
     WillBeHeapVector<RuleData> m_allRules;
 #endif
 };
 
 } // namespace blink
 
 WTF_ALLOW_MOVE_AND_INIT_WITH_MEM_FUNCTIONS(blink::RuleData);
 WTF_ALLOW_MOVE_AND_INIT_WITH_MEM_FUNCTIONS(blink::MinimalRuleData);
 
 #endif // RuleSet_h