NetworkStateNotifier: also remove NetworkStateObserver in finalizer too

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
@@ skipping 388 matching lines @@
 }
 
 static void recordLoadReasonToHistogram(WouldLoadReason reason) {
   DEFINE_STATIC_LOCAL(
       EnumerationHistogram, unseenFrameHistogram,
       ("Navigation.DeferredDocumentLoading.StatesV3", WouldLoadReasonEnd));
   unseenFrameHistogram.count(reason);
 }
 
 class Document::NetworkStateObserver final
-    : public GarbageCollected<Document::NetworkStateObserver>,
+    : public GarbageCollectedFinalized<Document::NetworkStateObserver>,
       public NetworkStateNotifier::NetworkStateObserver,
       public ContextLifecycleObserver {
   USING_GARBAGE_COLLECTED_MIXIN(Document::NetworkStateObserver);
+  EAGERLY_FINALIZE();
 
  public:
   explicit NetworkStateObserver(Document& document)
       : ContextLifecycleObserver(&document) {
     networkStateNotifier().addOnLineObserver(
         this,
         TaskRunnerHelper::get(TaskType::Networking, getExecutionContext()));
   }
 
+  // We eagerly finalize, so it's safe to touch getExecutionContext() here.
+  ~NetworkStateObserver() { unregisterAsObserver(getExecutionContext()); }
+
   void onLineStateChange(bool onLine) override {
     AtomicString eventName =
         onLine ? EventTypeNames::online : EventTypeNames::offline;
     Document* document = toDocument(getExecutionContext());
     if (!document->domWindow())
       return;
     document->domWindow()->dispatchEvent(Event::create(eventName));
     InspectorInstrumentation::networkStateChanged(document->frame(), onLine);
   }
 
   void contextDestroyed(ExecutionContext* context) override {
+    unregisterAsObserver(context);
+  }
+
+  void unregisterAsObserver(ExecutionContext* context) {
+    if (!context)
+      return;
     networkStateNotifier().removeOnLineObserver(
         this, TaskRunnerHelper::get(TaskType::Networking, context));
   }
 
   DEFINE_INLINE_VIRTUAL_TRACE() { ContextLifecycleObserver::trace(visitor); }
 };
 
 Document::Document(const DocumentInit& initializer,
                    DocumentClassFlags documentClasses)
     : ContainerNode(0, CreateDocument),
@@ skipping 6209 matching lines @@
 }
 
 void showLiveDocumentInstances() {
   WeakDocumentSet& set = liveDocumentSet();
   fprintf(stderr, "There are %u documents currently alive:\n", set.size());
   for (blink::Document* document : set)
     fprintf(stderr, "- Document %p URL: %s\n", document,
             document->url().getString().utf8().data());
 }
 #endif