Oilpan: move node/element rare data objects to the heap.

Source/core/dom/MutationObserverRegistration.h

Index: Source/core/dom/MutationObserverRegistration.h
diff --git a/Source/core/dom/MutationObserverRegistration.h b/Source/core/dom/MutationObserverRegistration.h
index 7668c09b115c78a31a385dd3a26cf3a0bc468d6c..7af8e85137f256db9dd7511c2f99d56d5aaac400 100644
--- a/Source/core/dom/MutationObserverRegistration.h
+++ b/Source/core/dom/MutationObserverRegistration.h
@@ -43,7 +43,7 @@ class QualifiedName;
 
 class MutationObserverRegistration FINAL : public NoBaseWillBeGarbageCollectedFinalized<MutationObserverRegistration> {
 public:
-    static PassOwnPtrWillBeRawPtr<MutationObserverRegistration> create(MutationObserver&, Node&, MutationObserverOptions, const HashSet<AtomicString>& attributeFilter);
+    static PassOwnPtrWillBeRawPtr<MutationObserverRegistration> create(MutationObserver&, Node*, MutationObserverOptions, const HashSet<AtomicString>& attributeFilter);
     ~MutationObserverRegistration();
 
     void resetObservation(MutationObserverOptions, const HashSet<AtomicString>& attributeFilter);
@@ -66,11 +66,11 @@ public:
     void dispose();
 
 private:
-    MutationObserverRegistration(MutationObserver&, Node&, MutationObserverOptions, const HashSet<AtomicString>& attributeFilter);
+    MutationObserverRegistration(MutationObserver&, Node*, MutationObserverOptions, const HashSet<AtomicString>& attributeFilter);
 
     RefPtrWillBeMember<MutationObserver> m_observer;
-    Node& m_registrationNode;
-    RefPtr<Node> m_registrationNodeKeepAlive;
+    RawPtrWillBeWeakMember<Node> m_registrationNode;
+    RefPtrWillBeMember<Node> m_registrationNodeKeepAlive;
     typedef HashSet<RefPtr<Node> > NodeHashSet;
     OwnPtr<NodeHashSet> m_transientRegistrationNodes;