[WIP] do something :-)

Source/core/dom/ElementRareData.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 14 matching lines @@
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "core/dom/ElementRareData.h"
 
 #include "core/style/ComputedStyle.h"
+#include "wtf/SizeAssertions.h"
 
 namespace blink {
 
-struct SameSizeAsElementRareData : NodeRareData {
-    short indices[2];
-    LayoutSize sizeForResizing;
-    IntSize scrollOffset;
-    void* pointers[13];
-};
+ASSERT_SIZE(ElementRareData, 88, 152);
 
 CSSStyleDeclaration& ElementRareData::ensureInlineCSSStyleDeclaration(Element* ownerElement)
 {
     if (!m_cssomWrapper)
         m_cssomWrapper = adoptPtrWillBeNoop(new InlineCSSStyleDeclaration(ownerElement));
     return *m_cssomWrapper;
 }
 
 AttrNodeList& ElementRareData::ensureAttrNodeList()
 {
@@ skipping 14 matching lines @@
     visitor->trace(m_elementAnimations);
     visitor->trace(m_cssomWrapper);
     visitor->trace(m_customElementDefinition);
     visitor->trace(m_generatedBefore);
     visitor->trace(m_generatedAfter);
     visitor->trace(m_generatedFirstLetter);
     visitor->trace(m_backdrop);
     NodeRareData::traceAfterDispatch(visitor);
 }
 
-static_assert(sizeof(ElementRareData) == sizeof(SameSizeAsElementRareData), "ElementRareData should stay small");
-
 } // namespace blink