Keep a strong handle to an event listener during handleEvent

Source/bindings/dart/DartEventListener.cpp

Index: Source/bindings/dart/DartEventListener.cpp
diff --git a/Source/bindings/dart/DartEventListener.cpp b/Source/bindings/dart/DartEventListener.cpp
index 92602dedbb3295a30d6986a826fc9259a71e6933..95f21e9e9f3de58d111021fd693366cc99ca2d73 100644
--- a/Source/bindings/dart/DartEventListener.cpp
+++ b/Source/bindings/dart/DartEventListener.cpp
@@ -96,6 +96,8 @@ void DartEventListener::handleEvent(ScriptExecutionContext* context, Event* even
     // 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);
@@ -103,7 +105,7 @@ void DartEventListener::handleEvent(ScriptExecutionContext* context, Event* even
 
     // 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;
@@ -130,16 +132,16 @@ EventListener* DartEventListener::toNative(Dart_Handle handle, Dart_Handle& exce
     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);
 }
 
 }