CB-5583 WebView doesn't properly initialize when instantiated from a xib

Limit createGapView to create and position webView, configure delegate
and register with NSURLProtocol in viewDidLoad.  When `self.webView` is
created outside this class (e.g. created from Nib) then `viewDidLoad`
won't properly configure the webView's `delegate` or register with
`NSURLProtocol` properly.