This might be related to [bug 1435343](https://bugzilla.mozilla.org/show_bug.cgi?id=1435343#c71): The `Dispatch()` function returns false and [GetSubscriptionResultRunnable](https://searchfox.org/mozilla-central/rev/55a4faa52f72918efa51150d127aebdc057dc6cf/dom/push/PushManager.cpp#94) derives from `WorkerRunnable`, which implements a suspicious `PreDispatch()`.
Bug 1633469 Comment 2 Edit History
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This might be related to [bug 1435343](https://bugzilla.mozilla.org/show_bug.cgi?id=1435343#c71): The `Dispatch()` function returns false and [GetSubscriptionResultRunnable](https://searchfox.org/mozilla-central/rev/55a4faa52f72918efa51150d127aebdc057dc6cf/dom/push/PushManager.cpp#94) derives from `WorkerRunnable`, which implements a suspicious `PreDispatch()`. Edit: Suspicious probably only in the shutdown case, where we might see a race between the main thread and the worker thread? I remember to have seen some assertions that indicate something like this on a different bug, need to check back.