Fired when an update to the extension is available. This event enables an extension to delay an update: for example, because it is in the middle of some operation which should not be interrupted.
If the extension is not listening for this event when an update becomes available, the extension is reloaded immediately and the update is applied. If the extension is listening, then the update will be applied the next time the extension is reloaded. This happens if:
- the browser is restarted
- the extension is disabled and re-enabled
- the extension explicitly reloads itself by calling
runtime.reload().