Make hang triggering more deterministic (#5413)

Author: noahsmartin

Samples/iOS-Swift/iOS-Swift/Tools/TriggerAppHang.swift

@@ -20,18 +20,7 @@ func triggerNonFullyBlockingAppHang() {
     }
 }
 
-/// Schedules heavy UI rendering work on the main thread in a tight loop, which causes
-/// a fully blocking app hang without frames being rendered.
+/// Sleep on the main thread for long enough to trigger a hang
 func triggerFullyBlockingAppHang(button: UIButton) {
-    let buttonTitle = button.currentTitle
-    var i = 0
-
-    for _ in 0...5_000_000 {
-        i += Int.random(in: 0...10)
-        i -= 1
-
-        button.setTitle("\(i)", for: .normal)
-    }
-
-    button.setTitle(buttonTitle, for: .normal)
+  sleep(5)
 }