Example of how to use CustomWKWebView.

ViewController.swift

import UIKit
import WebKit

class ViewController: UIViewController, CustomWKWebDelegate, WKNavigationDelegate, URLSessionDownloadDelegate {
    
    var testWeb: CustomWKWebView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        let webFrameY: CGFloat = 20
        let webFrameWidth = self.view.frame.width
        let webFrameHeight = self.view.frame.height - webFrameY
        let webFrame = CGRect(x: 0, y: webFrameY, width: webFrameWidth, height: webFrameHeight)
        testWeb = CustomWKWebView(frame: webFrame)
        testWeb.delegate = self
        testWeb.navigationDelegate = self
        self.view.addSubview(testWeb)
        
        testWeb.loadURL(url: "http://www.google.com")
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        testWeb.getIconImage()
    }
    
    func urlDidGet(customWebView: CustomWKWebView, arrURL: [URL]) {
        if arrURL.isEmpty == false{
            for temp in arrURL{
                download(url: temp)
            }
        }
    }
    
    func download(url: URL?){
        guard let url = url else{print("canceled"); return}
        let defaultSession = URLSession(configuration: URLSessionConfiguration.default, delegate: self, delegateQueue: nil)
        let task = defaultSession.downloadTask(with: url)
        task.resume()
    }
    
    func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
        print("Downloaded: \(location)")
        var image: UIImage?
        do{
            let data = try Data(contentsOf: location)
            image = UIImage(data: data)
        }catch let error as NSError{
            print(error)
        }
    }
    
}