This is happening on ash on osx debug, pretty frequently after random bc/dt tests with 4 content process enabled. https://treeherder.mozilla.org/#/jobs?repo=ash&selectedJob=77442099

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The assertion happens when a lock is destroyed while it's still being hold. Since this kind of lock is used in multiple places, Core/General seems to be the correct component, because we don't have any STR or stack trace to further narrow down the cause of this assertion error.