Oh, now I understand why bug 1522244 added that, it's not not as easy as I thought. test_objectgrips-20.js passes with my patch because there aren't xrays, but steps in comment 0 still don't work because there is an Opaque wrapper.
Bug 1547320 Comment 3 Edit History
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Oh, now I understand why bug 1522244 added that, it's not not as easy as I thought. test_objectgrips-20.js passes for workers with my patch, but steps in comment 0 still don't work...