The webView should reload when a crash occurs (iOS 8)

When the WKProcess dies, the content is blanked out and the URL becomes nil. This results in a "white screen" that can only be resolved by restarting the app. See this for more info: https://bugs.webkit.org/show_bug.cgi?id=148685

With the iOS9 API, it is now possible to detect when the WKProcess dies. On iOS 8, we can listen for changes on URL of the WKWebView to be notified when it crashes.