The attached patch (just trying one additional more-direct "please give me your baseline" API) fixes both testcases here, as well as the testcases on see-also bug 1686961.
Bug 1672640 Comment 12 Edit History
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The attached patch (just trying one additional more-direct "please give me your baseline" API) fixes both testcases here ~as well as the testcases on see-also bug 1686961~ [EDIT: just kidding, this doesn't help with bug 1686961's testcases after all -- a different diagnostic-patch in my stack was helping with those in my local test]