This app appears to be a website-to-PDF converter. There's a gray address bar at the top. It allows you to take screenshots of apple.com. This is probably not an InternalUI application. It's used for the "Full Page" view in the screenshot viewer. However, if you take a screenshot of a website and tap on the image, a simplified version of the app will appear, which is integrated into the screenshot viewer when you take an image of a webpage or PDF and tap "Full Page" at the top.