title: Error When using "WKAudiovisualMediaTypeNone" in Swift 3
body: <p>Trying to add <code>WKAudiovisualMediaTypeNone</code> to <code>mediaTypesRequiringUserActionForPlayback</code> for a <code>WKWebview</code>. But I can't get it to work. </p>
  
  <p><strong>Error</strong></p>
  
  <blockquote>
    <p>"Use of unresolved identifier 'WKaudiovisualMediaTypeNone'"</p>
  </blockquote>
  
  <p><strong>in this context</strong></p>
  
  <pre><code>required init?(coder aDecoder: NSCoder) {
      let webConfiguration = WKWebViewConfiguration()
      webConfiguration.allowsInlineMediaPlayback = true
      webConfiguration.mediaTypesRequiringUserActionForPlayback = WKAudiovisualMediaTypeNone; // Error getting here
      self.webView = WKWebView(frame: CGRectZero, configuration: webConfiguration) 
      super.init(coder: aDecoder)
  }
  </code></pre>
  
  <p>Please help</p>