We have code in onDestroy() that sends a shutdown event to Gecko, where presumably we're doing some cleanup or persisting things to disk. From https://bugzilla.mozilla.org/show_bug.cgi?id=823285#c21: We're trying to force a simple open/close desktop application model onto Android, but we simply have no reliable way to know when we're closing. I think the way to fix this would be to not rely on executing a shutdown event at all, but to instead make sure that all necessary data is saved when we receive onPause() (which would likely overlap the part of shutdown logic that persists data, but not the part that finishes Gecko). Several critical I/O components - session restore, disk cache, and prefs - already do this. I don't know if there are other essential components that need to flush to disk as well, but if there are, they aren't working now anyway.

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