"onVisibleBehindCanceled" is deprecated in Android O

Hi,

I notice the file "PlaybackOverlayActivity.java" overrides "onVisibleBehindCanceled", which is deprecated in Android O (link). As the official document says, "onVisibleBehindCanceled" cannot get chance to execute since Android O and will be removed in the future release.

So you may prevent putting some important operations in it.

Hope the information can help you. :)