chromium/third_party/blink/web_tests/fast/events/tab-focus-link-in-canvas.html

<!DOCTYPE html>
<html>
<head>
<script src="../../resources/js-test.js"></script>
</head>
<body>

<a id="before" href="#">Before</a>

<canvas>
  <a id="canvas_link" href="#">Canvas Link</a>
</canvas>

<script>
description("Ensures that you can tab to focus a link inside a canvas subtree.");

if (window.testRunner && window.eventSender) {
    testRunner.dumpAsText();
    testRunner.overridePreference("WebKitTabToLinksPreferenceKey", 1);

    document.getElementById('before').focus();
    shouldBe('document.activeElement.id', '"before"');

    eventSender.keyDown('\t');
    shouldBe('document.activeElement.id', '"canvas_link"');
}

</script>
</body>
</html>