Reduce a shadow root object's size by not inheriting DoublyLinkedList

third_party/WebKit/Source/core/dom/shadow/ShadowRootRareDataV0.h

 /*
  * Copyright (C) 2013 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 41 matching lines @@
 
     bool containsShadowElements() const { return m_descendantShadowElementCount; }
     bool containsContentElements() const { return m_descendantContentElementCount; }
 
     unsigned descendantShadowElementCount() const { return m_descendantShadowElementCount; }
 
     const HeapVector<Member<InsertionPoint>>& descendantInsertionPoints() { return m_descendantInsertionPoints; }
     void setDescendantInsertionPoints(HeapVector<Member<InsertionPoint>>& list) { m_descendantInsertionPoints.swap(list); }
     void clearDescendantInsertionPoints() { m_descendantInsertionPoints.clear(); }
 
+    void setYoungerShadowRoot(ShadowRoot& youngerShadowRoot) { m_youngerShadowRoot = &youngerShadowRoot; }
+    void setOlderShadowRoot(ShadowRoot& olderShadowRoot) { m_olderShadowRoot = &olderShadowRoot; }
+
+    ShadowRoot* youngerShadowRoot() const { return m_youngerShadowRoot; }
+    ShadowRoot* olderShadowRoot() const { return m_olderShadowRoot; }
+
     DEFINE_INLINE_TRACE()
     {
+        visitor->trace(m_youngerShadowRoot);
+        visitor->trace(m_olderShadowRoot);
         visitor->trace(m_shadowInsertionPointOfYoungerShadowRoot);
         visitor->trace(m_descendantInsertionPoints);
     }
 
 private:
+    Member<ShadowRoot> m_youngerShadowRoot;
+    Member<ShadowRoot> m_olderShadowRoot;
     Member<HTMLShadowElement> m_shadowInsertionPointOfYoungerShadowRoot;
     unsigned m_descendantShadowElementCount;
     unsigned m_descendantContentElementCount;
     HeapVector<Member<InsertionPoint>> m_descendantInsertionPoints;
 };
 
 inline void ShadowRootRareDataV0::didAddInsertionPoint(InsertionPoint* point)
 {
     DCHECK(point);
     if (isHTMLShadowElement(*point))
@@ skipping 14 matching lines @@
         DCHECK_GT(m_descendantContentElementCount, 0u);
         --m_descendantContentElementCount;
     } else {
         ASSERT_NOT_REACHED();
     }
 }
 
 } // namespace blink
 
 #endif