Oilpan: Make the Node hierarchy RefCountedGarbageCollected instead of TreeShared.

Source/core/dom/IdTargetObserver.cpp

Index: Source/core/dom/IdTargetObserver.cpp
diff --git a/Source/core/dom/IdTargetObserver.cpp b/Source/core/dom/IdTargetObserver.cpp
index af185a0ad05e3f1e0ec151c32160a60d76acfb46..50294e4db3c126fa2ae91c6443ea4b9a04610f5d 100644
--- a/Source/core/dom/IdTargetObserver.cpp
+++ b/Source/core/dom/IdTargetObserver.cpp
@@ -39,7 +39,16 @@ IdTargetObserver::IdTargetObserver(IdTargetObserverRegistry& registry, const Ato
 
 IdTargetObserver::~IdTargetObserver()
 {
+#if !ENABLE(OILPAN)
     m_registry.removeObserver(m_id, this);
+#endif
+}
+
+void IdTargetObserver::unregister()
+{
+#if ENABLE(OILPAN)
+    m_registry.removeObserver(m_id, this);
+#endif
 }
 
 } // namespace WebCore