Oilpan: have LifetimeNotifier<T> track its observers weakly.

Source/core/dom/ActiveDOMObject.cpp

 /*
  * Copyright (C) 2008 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 34 matching lines @@
     // ActiveDOMObject may be inherited by a sub-class whose life-cycle
     // exceeds that of the associated ExecutionContext. In those cases,
     // m_executionContext would/should have been nullified by
     // ContextLifecycleObserver::contextDestroyed() (which we implement /
     // inherit). Hence, we should ensure that this is not 0 before use it
     // here.
     if (!executionContext())
         return;
 
     ASSERT(m_suspendIfNeededCalled);
+#if !ENABLE(OILPAN)
     ASSERT(executionContext()->isContextThread());
+#endif
 }
 
 void ActiveDOMObject::suspendIfNeeded()
 {
 #if ENABLE(ASSERT)
     ASSERT(!m_suspendIfNeededCalled);
     m_suspendIfNeededCalled = true;
 #endif
     if (ExecutionContext* context = executionContext())
         context->suspendActiveDOMObjectIfNeeded(this);
@@ skipping 27 matching lines @@
 
     if (context->activeDOMObjectsAreSuspended()) {
         suspend();
         return;
     }
 
     resume();
 }
 
 } // namespace blink