Improve DEFINE_STATIC_LOCAL()'s handling of Blink GCed objects.

third_party/WebKit/Source/core/dom/MutationObserver.cpp

Index: third_party/WebKit/Source/core/dom/MutationObserver.cpp
diff --git a/third_party/WebKit/Source/core/dom/MutationObserver.cpp b/third_party/WebKit/Source/core/dom/MutationObserver.cpp
index 9b7a0d9c99098720d06a562e3b37807e82b52b87..5ba305a1067c2855facb56d94d4f3cdd3ace9420 100644
--- a/third_party/WebKit/Source/core/dom/MutationObserver.cpp
+++ b/third_party/WebKit/Source/core/dom/MutationObserver.cpp
@@ -166,14 +166,14 @@ void MutationObserver::observationEnded(MutationObserverRegistration* registrati
 
 static MutationObserverSet& activeMutationObservers()
 {
-    DEFINE_STATIC_LOCAL(Persistent<MutationObserverSet>, activeObservers, (new MutationObserverSet()));
-    return *activeObservers;
+    DEFINE_STATIC_LOCAL(MutationObserverSet, activeObservers, (new MutationObserverSet));
+    return activeObservers;
 }
 
 static MutationObserverSet& suspendedMutationObservers()
 {
-    DEFINE_STATIC_LOCAL(Persistent<MutationObserverSet>, suspendedObservers, (new MutationObserverSet()));
-    return *suspendedObservers;
+    DEFINE_STATIC_LOCAL(MutationObserverSet, suspendedObservers, (new MutationObserverSet));
+    return suspendedObservers;
 }
 
 static void activateObserver(RawPtr<MutationObserver> observer)