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

Source/bindings/core/v8/ScriptPromiseResolver.h

Index: Source/bindings/core/v8/ScriptPromiseResolver.h
diff --git a/Source/bindings/core/v8/ScriptPromiseResolver.h b/Source/bindings/core/v8/ScriptPromiseResolver.h
index ac8239b4a2ec04ec8869542b558e839d1891f438..6af0ff44cb364f90c211cc6300a0e535a87015a9 100644
--- a/Source/bindings/core/v8/ScriptPromiseResolver.h
+++ b/Source/bindings/core/v8/ScriptPromiseResolver.h
@@ -117,11 +117,6 @@ private:
         // This function cannot be run in the destructor if
         // ScriptPromiseResolver is on-heap.
         ASSERT(m_state == ResolvedOrRejected || !m_isPromiseCalled || !executionContext() || executionContext()->activeDOMObjectsAreStopped());
-
-#if ENABLE(OILPAN)
-        // Delegate to LifecycleObserver's prefinalizer.
-        LifecycleObserver::dispose();
-#endif
     }
 #endif