https://archimboldi.me/posts/%E7%BF%BB%E8%AF%91-uidebugginginformationoverlay.html
http://ryanipete.com/blog/ios/swift/objective-c/uidebugginginformationoverlay/
let overlayClass = NSClassFromString("UIDebuggingInformationOverlay") as? UIWindow.Type
_ = overlayClass?.perform(NSSelectorFromString("prepareDebuggingOverlay"))
app启动后, 在statusbar上双指点击即可调出.
发布时记得要删除这个功能. 可能会被拒绝.