Assembly: Microsoft.Phone (in Microsoft.Phone.dll)
XMLNS for XAML: Not mapped to an xmlns.
In the Windows Phone 8.1 WebBrowser control, the event has changed to be an asynchronous event. It was previously a synchronous event in Windows Phone 8 Silverlight apps. If a Windows Phone 8 Silverlight app is run on Windows Phone 8.1, the behavior change in from synchronous to asynchronous will cause apps to execute differently.