package webextension_polyfill.webrequest; /** Fired when an error occurs. **/ typedef OnErrorOccurredEvent = { /** Registers an event listener callback to an event. **/ function addListener(callback:(details:OnErrorOccurredDetailsType) -> Void, filter:RequestFilter, ?extraInfoSpec:Array):Void; /** Deregisters an event listener callback from an event. **/ function removeListener(callback:(details:OnErrorOccurredDetailsType) -> Void):Void; function hasListener(callback:(details:OnErrorOccurredDetailsType) -> Void):Bool; function hasListeners():Bool; };