Have ChildFrameDisconnector / ChildListMutationScope deal with references

Source/core/dom/MutationObserverInterestGroup.cpp

Index: Source/core/dom/MutationObserverInterestGroup.cpp
diff --git a/Source/core/dom/MutationObserverInterestGroup.cpp b/Source/core/dom/MutationObserverInterestGroup.cpp
index 7169bb25bab55378ec32040330b62d9f5a412937..48cd761d29c8e07406f5d66af11194b8ab96900e 100644
--- a/Source/core/dom/MutationObserverInterestGroup.cpp
+++ b/Source/core/dom/MutationObserverInterestGroup.cpp
@@ -38,11 +38,11 @@
 
 namespace WebCore {
 
-PassOwnPtr<MutationObserverInterestGroup> MutationObserverInterestGroup::createIfNeeded(Node* target, MutationObserver::MutationType type, MutationRecordDeliveryOptions oldValueFlag, const QualifiedName* attributeName)
+PassOwnPtr<MutationObserverInterestGroup> MutationObserverInterestGroup::createIfNeeded(Node& target, MutationObserver::MutationType type, MutationRecordDeliveryOptions oldValueFlag, const QualifiedName* attributeName)
 {
     ASSERT((type == MutationObserver::Attributes && attributeName) || !attributeName);
     HashMap<MutationObserver*, MutationRecordDeliveryOptions> observers;
-    target->getRegisteredMutationObserversOfType(observers, type, attributeName);
+    target.getRegisteredMutationObserversOfType(observers, type, attributeName);
     if (observers.isEmpty())
         return nullptr;