Keep a strong handle to an event listener during handleEvent

Source/bindings/dart/DartEventListener.cpp

 /*
  * Copyright (C) 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 78 matching lines @@
         return;
 
     ASSERT(event);
 
     DartIsolateScope scope(m_isolate);
     DartApiScope apiScope;
 
     // The callback function on XMLHttpRequest can clear the event listener and destroys 'this' object. Keep a local reference to it.
     // See issue 889829.
     RefPtr<DartEventListener> protect(this);
+    // Keep a strong handle to the listener.
+    Dart_Handle listener = Dart_HandleFromWeakPersistent(m_listener);
 
     // Get the Dart wrapper for the event object.
     Dart_Handle dartEvent = DartEvent::toDart(event);
     ASSERT(dartEvent);
 
     // FIXME: consider if DateExtension manipulations are necessary and if yes (most probably),
     // factor out common logic. For example by introducing EventProcessScope RAII to manage DateExtension.
-    Dart_Handle result = callListenerFunction(context, dartEvent, event);
+    Dart_Handle result = callListenerFunction(context, listener, dartEvent);
     if (Dart_IsError(result)) {
         DartUtilities::reportProblem(context, result);
         return;
     }
 
     if (Dart_IsString(result)) {
         if (event->storesResultAsString())
             event->storeResult(DartUtilities::toString(result));
     }
 }
 
 EventListener* DartEventListener::toNative(Dart_Handle handle, Dart_Handle& exception)
 {
     if (Dart_IsNull(handle)) {
         exception = Dart_NewStringFromCString("Null passed where Dart closure is expected");
         return 0;
     }
 
     if (!Dart_IsClosure(handle)) {
         exception = Dart_NewStringFromCString("Not a Dart closure passed");
         return 0;
     }
 
     return createOrFetch(handle);
 }
 
-Dart_Handle DartEventListener::callListenerFunction(ScriptExecutionContext* context, Dart_Handle dartEvent, Event* event)
+Dart_Handle DartEventListener::callListenerFunction(ScriptExecutionContext* context, Dart_Handle listener, Dart_Handle dartEvent)
 {
-    ASSERT(m_listener);
+    ASSERT(listener);
 
     DartController* dartController = DartController::retrieve(context);
     if (!dartController)
         return Dart_Error("Internal error: failed to fetch Dart controller");
 
     Dart_Handle parameters[1] = { dartEvent };
-    return dartController->callFunction(Dart_HandleFromWeakPersistent(m_listener), 1, parameters);
+    return dartController->callFunction(listener, 1, parameters);
 }
 
 }