+ * This allows code to perform tasks in the main thread without impacting
+ * time-critical operations such as animations and response to input events.
+ *
+ * Basic logic is as follows:
+ *
+ * - User input event should be acknowledged within 100ms per [RAIL].
+ * - Idle work should be grouped in blocks of upto 50ms so that enough time
+ * remains for the event handler to execute and any rendering to take place.
+ * - Whenever a native event happens (e.g. user input), the deadline for any
+ * running idle callback drops to 0.
+ * - As long as the deadline is non-zero, other callbacks pending may be
+ * executed in the same idle period.
+ *
+ * See also:
+ *
+ * - <https://developer.mozilla.org/en-US/docs/Web/API/Window/requestIdleCallback>
+ * - <https://w3c.github.io/requestidlecallback/>
+ * - <https://developers.google.com/web/updates/2015/08/using-requestidlecallback>
+ * [RAIL]: https://developers.google.com/web/fundamentals/performance/rail
+ *