     private var toolbarContainer: GDWebViewNavigationToolbar!
     private var toolbarHeightConstraint: NSLayoutConstraint!
     private var toolbarHeight: CGFloat = 0
+    private var navControllerUsesBackSwipe: Bool = false
     
     // MARK: Public Methods
     

        webView.removeObserver(self, forKeyPath: "title")
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        webView.stopLoading()

    }
    
    private func backForwardListChanged() {
        if self.navControllerUsesBackSwipe && self.allowsBackForwardNavigationGestures {
            self.navigationController?.interactivePopGestureRecognizer.enabled = !webView.canGoBack
        }
        
