Replaced Blocking Sleep with Non-blocking Delay

I am a PhD student in the CS department at the University of Illinois. I'm currently doing research on asynchronous programming in phone applications. I developed a tool that automatically improves async/await usages by doing transformations.

The tool found some opportunities in your application. You were using blocking Sleep method in an async method, causing freezing the UI. Instead, you can use nonblocking Task.Delay for the same purpose. The tool changed Sleep method with Delay method. 

Are you interested in merging this pull request? If not, please let me know why.

Thanks for your time,