LayoutTests/fast/css/text-scale/parsing-flag-runtime-toggle.html

<!DOCTYPE html><!-- webkit-test-runner [ CSSTextScaleMetaEnabled=false ] -->
<html>
<head>
<meta charset="utf-8">
<meta name="text-scale" content="scale">
<link rel="help" href="https://drafts.csswg.org/css-fonts-5/#text-scale-meta">
<script src="../../../resources/testharness.js"></script>
<script src="../../../resources/testharnessreport.js"></script>
</head>
<body>
<script>
test(() => {
    assert_equals(internals.textScaleMetaMode(), "legacy");
    internals.settings.setCSSTextScaleMetaEnabled(true);
    assert_equals(internals.textScaleMetaMode(), "scale");
    internals.settings.setCSSTextScaleMetaEnabled(false);
    assert_equals(internals.textScaleMetaMode(), "legacy");
}, "Toggling the flag at runtime updates the mode without a meta change");
</script>
</body>
</html>