LayoutTests/fast/canvas/canvas-css-size-after-height-change-with-display-flex.html

<div style="display: flex; flex-direction: column;">
    <canvas style="background-color: blue; max-width: 600px">
        <script>
            if (window.testRunner)
                testRunner.waitUntilDone();

            window.requestAnimationFrame(function() {
                document.querySelector("canvas").height = "300";
                if (window.testRunner)
                    testRunner.notifyDone();
            });
        </script>
    </canvas>
</div>