LayoutTests/plugins/snapshot-appearance.html

<!-- Since we're not a snapshotted plugin, this test should do nothing (and not crash) -->
<style>
div {
    width: 50px;
    height: 50px;
    background-color: blue;
}

#snapshot {
    -webkit-appearance: snapshotted-plugin-overlay;
}
</style>
<div id="normal"></div>
<div id="snapshot"></div>