Explicit notification and removal of lifecycle observers.

Source/core/workers/WorkerGlobalScope.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2009, 2011 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 75 matching lines @@
     , m_timeOrigin(timeOrigin)
 {
     ScriptWrappable::init(this);
     setClient(this);
     setSecurityOrigin(SecurityOrigin::create(url));
     m_workerClients->reattachThread();
 }
 
 WorkerGlobalScope::~WorkerGlobalScope()
 {
-#if !ENABLE(OILPAN)
-    dispose();
-#endif
 }
 
 void WorkerGlobalScope::applyContentSecurityPolicyFromString(const String& policy, ContentSecurityPolicyHeaderType contentSecurityPolicyType)
 {
     setContentSecurityPolicy(ContentSecurityPolicy::create(this));
     contentSecurityPolicy()->didReceiveHeader(policy, contentSecurityPolicyType, ContentSecurityPolicyHeaderSourceHTTP);
 }
 
 ExecutionContext* WorkerGlobalScope::executionContext() const
 {
@@ skipping 80 matching lines @@
 
 void WorkerGlobalScope::willStopActiveDOMObjects()
 {
     lifecycleNotifier().notifyWillStopActiveDOMObjects();
 }
 
 void WorkerGlobalScope::dispose()
 {
     ASSERT(thread()->isCurrentThread());
 
-    // Notify proxy that we are going away. This can free the WorkerThread object, so do not access it after this.
-    thread()->workerReportingProxy().workerGlobalScopeDestroyed();
-
     clearScript();
     clearInspector();
     setClient(0);
 
-    // The thread reference isn't currently cleared, as the execution
-    // context's thread is accessed by GCed lifetime objects when
-    // they're finalized.
-    // FIXME: oilpan: avoid by explicitly removing the WorkerGlobalScope
-    // as an observable context right here.
+    // Observers must not access the context of a disposed WorkerGlobalScope
+    // lacking a thread object.
+    //
+    // Notify them now that the context has been destroyed and explicitly remove
+    // them as observers. If this is delayed until the LifecycleNotifier of the
+    // WorkerGlobalScope is garbage collected and destructed, some observers
+    // may have access to the disposed object (it all depends on the order
+    // the garbage collector finalizes these objects.) Prevent that situation from
+    // arising here.
+    removeAllLifecycleObservers();
+    clearThread();
 }
 
 void WorkerGlobalScope::importScripts(const Vector<String>& urls, ExceptionState& exceptionState)
 {
     ASSERT(contentSecurityPolicy());
     Vector<String>::const_iterator urlsEnd = urls.end();
     Vector<KURL> completedURLs;
     for (Vector<String>::const_iterator it = urls.begin(); it != urlsEnd; ++it) {
         const KURL& url = executionContext()->completeURL(*it);
         if (!url.isValid()) {
@@ skipping 84 matching lines @@
 {
     visitor->trace(m_console);
     visitor->trace(m_location);
     visitor->trace(m_navigator);
 #if ENABLE(OILPAN)
     HeapSupplementable<WorkerGlobalScope>::trace(visitor);
 #endif
 }
 
 } // namespace WebCore