Add assert to catch dispatching events over dying targets.

third_party/WebKit/Source/core/events/EventTarget.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  *           (C) 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ skipping 257 matching lines @@
 }
 
 bool EventTarget::dispatchEvent(PassRefPtrWillBeRawPtr<Event> event)
 {
     event->setTrusted(true);
     return dispatchEventInternal(event);
 }
 
 bool EventTarget::dispatchEventInternal(PassRefPtrWillBeRawPtr<Event> event)
 {
+#if ENABLE(OILPAN)
+    // Dispatching events for a target that is about to be swept,
+    // is unsafe and not allowed. If this assert triggers, your
+    // EventTarget needs to extend its lifetime accordingly.
+    // Using mechanisms like e.g., ActiveDOMObject::hasPendingActivity().
+    ASSERT(!Heap::willObjectBeLazilySwept(this));
+#endif
     event->setTarget(this);
     event->setCurrentTarget(this);
     event->setEventPhase(Event::AT_TARGET);
     bool defaultWasNotPrevented = fireEventListeners(event.get());
     event->setEventPhase(0);
     return defaultWasNotPrevented;
 }
 
 void EventTarget::uncaughtExceptionInEventHandler()
 {
@@ skipping 188 matching lines @@
     // they have one less listener to invoke.
     if (d->firingEventIterators) {
         for (size_t i = 0; i < d->firingEventIterators->size(); ++i) {
             d->firingEventIterators->at(i).iterator = 0;
             d->firingEventIterators->at(i).end = 0;
         }
     }
 }
 
 } // namespace blink