title: WKWebView didFinishNavigation is not working with frame/iframes
body: <p>I am trying to load a html which has 2 frames in it using WKWebView. I am getting all the navigation delegates for main frame once but not getting didCommit and didFinish callback for subframes. </p>
  
  <p>My sample html is like this:</p>
  
  <pre><code>https://example.com &lt;html&gt;&lt;head&gt;&lt;base href="https://example.com"&gt;&lt;/head&gt;&lt;frameset framespacing="0" rows="*,0" frameborder="0" noresize&gt;&lt;frame name="sco" src="https://example.com//assets/s/uruq3acajh9u/x/mobile/path/loading.html"&gt;&lt;frame name="adaptor" src="https://example.com//assets/s/uruq3acajh9u/content/mobile/path/1.html?sco_url=https://example.com/content/elearningngx/VHDRczdEy5kO_pRfKsNJEA/1571433806/0088Z2lPcUR4MVljWWlPUVYvSjNrby9OVjJzbk84OENkN1h3SVl3UVBPMG9sb3lXNFFsaHUwT2xDbVhFTzVpMWdiNQ==RnJpIE9jdCAxOCAxMzoyMzoyNiBVVEMgMjAxOQ==/eot/index.html"&gt;&lt;/frameset&gt;&lt;/html&gt;
  
  func setupWebView(){  
          if (self.webView != nil){  
              self.webView.removeFromSuperview()  
          }  
  
          HTTPCookieStorage.shared.cookieAcceptPolicy = .always  
  
          let userContentController = WKUserContentController()  
          userContentController.addUserScript(HTMLViewScripts.viewportScript)  
  
  
          let pref = WKPreferences()  
          pref.javaScriptEnabled = true  
          pref.javaScriptCanOpenWindowsAutomatically = true  
          pref.setValue(true, forKey: "allowFileAccessFromFileURLs")  
          pref.setValue(true, forKey: "_allowUniversalAccessFromFileURLs")  
  
          let wkWebConfig = WKWebViewConfiguration()  
          wkWebConfig.preferences = pref  
          wkWebConfig.userContentController = userContentController  
  
          let wkWebSiteStore = WKWebsiteDataStore.nonPersistent()  
          wkWebConfig.websiteDataStore = wkWebSiteStore  
  
          self.webView = WKWebView(frame: CGRect(x: 0, y: 0, width: Constants.screenSize.width, height: self.playerContainer.frame.size.height), configuration: wkWebConfig)  
          self.webView.navigationDelegate = self  
          self.webView.uiDelegate = self  
          self.playerContainer.addSubview(self.webView)  
      }  
  </code></pre>
  
  <p>Also same issue with evaluateJavaScript as well. I am not getting any callback when loading "about:blank" using evaluateJavaScript. Seems same frames related issue.</p>
  
  <p>Any leads would be appriciated. Thanks in advance.</p>