The first time I saw that pattern was in Youtube where you could drag down the video to the corner and it would transition dow. I am just guessing that they're

The first time I saw that pattern was in Youtube where you could drag down the video to the corner and it would transition dow. I am just guessing that they're using a custom transition on a modal presentation and using UIPercentDrivenInteractiveTransition to let you drag it up or down.