Created attachment 354481 [details] Test case to reproduce the issue Steps to reproduce the issue: 1- load the attached test case What is the expected behavior? The grid case is rendered like the flexible box one. Firefox, Edge and Chrome have this behavior. What went wrong ? The grid row tracks are sized as if they were auto, ignoring the percentage value.
Since r272302, the test case shows up like the other browsers and the layout test is passing[1]. [1] https://results.webkit.org/?suite=layout-tests&test=fast%2Fcss-grid-layout%2Fpositioned-grid-container-percentage-tracks.html