Remove "external" flavor of workbox-window events

Library Affected: workbox-window

Browser & Platform: Chrome 72

Issue or Feature Request Description: If the service worker update is triggered from within the app using ServiceWorkerRegistration.update() instead of automatically at page load then the workbox-window events don’t work as they normally do, breaking the update mechanism which otherwise works as expected when used with normal app re-launch.

This would be useful for long-running devices where the trigger for a version check can be pushed out (e.g. by the device subscribing to firebase, having a notification sent etc…)

Will try to create a simplified reproduction.

[alex-stumpfl]

The problem seems to be, that the behaviour in case of ServiceWorkerRegistration.update() is not deterministic. Sometimes it works as expected (resulting in a ‘waiting’ event) while in other cases an ‘externalwaiting’ event is triggered instead. Couldn’t reproduce that consistently (so it’s pretty hard to test), but it primarily happens, when the page was offline for a while (by devtools or server shutdown) and became online again.

[jeffposnick]

In retrospect, I wonder if the externalwaiting vs. waiting distinction exposed in workbox-window has ended up being a net-positive for developers.

Perhaps moving forward, coalescing both into a single (presumably new) event would make sense? The separate events could still be maintained for backwards compatibility.

Alternatively, maybe we need to update our recipes to add in listeners for both waiting and externalwaiting, where we execute the same event handler for both.