The devices are all >= 9.1
This works in the Simulator, for videos and PDFs. On iOS devices, the PDFs load, but the videos (.mp4) do not. I get the circle + triangle that inspires confidence that a video can be played, but no video thumbnail is seen behind it, and tapping that circle-inscribed triangle does nothing!
webView.loadFileURL(uRL, allowingReadAccessToURL: uRL)