WebView control in Windows Store app is used to display HTML content such as a
URL. If you use a WebView control in your application, you will see your AppBar
or Charms are hidden behind the WebView control.
is because a WebView control is not really a XAML element and does not have
same events and rendering process as other XAML controls.
overcome this problem, Microsoft recommends to use a WebViewBrush.
is a good blog on the same: