[WIP] do something :-)

Source/core/dom/NodeRareData.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 18 matching lines @@
  */
 
 #include "config.h"
 #include "core/dom/NodeRareData.h"
 
 #include "core/dom/Element.h"
 #include "core/dom/ElementRareData.h"
 #include "core/frame/FrameHost.h"
 #include "core/layout/LayoutObject.h"
 #include "platform/heap/Handle.h"
+#include "wtf/SizeAssertions.h"
 
 namespace blink {
 
-struct SameSizeAsNodeRareData {
-    void* m_pointer[2];
-    OwnPtrWillBeMember<NodeMutationObserverData> m_mutationObserverData;
-    unsigned m_bitfields;
-};
-
-static_assert(sizeof(NodeRareData) == sizeof(SameSizeAsNodeRareData), "NodeRareData should stay small");
+ASSERT_SIZE(NodeRareData, 16, 32);
 
 DEFINE_TRACE_AFTER_DISPATCH(NodeRareData)
 {
     visitor->trace(m_mutationObserverData);
     // Do not keep empty NodeListsNodeData objects around.
     if (m_nodeLists && m_nodeLists->isEmpty())
         m_nodeLists.clear();
     else
         visitor->trace(m_nodeLists);
 }
@@ skipping 18 matching lines @@
 void NodeRareData::incrementConnectedSubframeCount(unsigned amount)
 {
     RELEASE_ASSERT_WITH_SECURITY_IMPLICATION((m_connectedFrameCount + amount) <= FrameHost::maxNumberOfFrames);
     m_connectedFrameCount += amount;
 }
 
 // Ensure the 10 bits reserved for the m_connectedFrameCount cannot overflow
 static_assert(FrameHost::maxNumberOfFrames < (1 << NodeRareData::ConnectedFrameCountBits), "Frame limit should fit in rare data count");
 
 } // namespace blink