constructor() {
        super();
        this._subscriptions = new DisposableStore();
        this._keyStatus = {
            altKey: false,
            shiftKey: false,
            ctrlKey: false,
            metaKey: false
        };
        this._subscriptions.add(event.Event.runAndSubscribe(onDidRegisterWindow, ({ window, disposables }) => this.registerListeners(window, disposables), { window: mainWindow, disposables: this._subscriptions }));
    }
List of safe, non-input html tags.