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

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

Index: third_party/WebKit/Source/core/dom/shadow/ShadowRootRareDataV0.h
diff --git a/third_party/WebKit/Source/core/dom/shadow/ShadowRootRareDataV0.h b/third_party/WebKit/Source/core/dom/shadow/ShadowRootRareDataV0.h
index c0f62d247576d495ed2339e7c024cda01eebdd69..6c7e0338e34d72eb0a58a2d96221ec51e60b3858 100644
--- a/third_party/WebKit/Source/core/dom/shadow/ShadowRootRareDataV0.h
+++ b/third_party/WebKit/Source/core/dom/shadow/ShadowRootRareDataV0.h
@@ -59,13 +59,23 @@ public:
     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;