chromium/third_party/blink/web_tests/plugins/invalid-mime-with-valid-extension-shows-missing-plugin.html

<script>
    if (window.testRunner) {
        testRunner.dumpAsText();
        testRunner.waitUntilDone();
    }

    function logFailure() {
        document.getElementById("console").innerHTML = "FAIL";
    }

    function finishTest() {
        if (window.testRunner)
            testRunner.notifyDone();
    }
</script>
<div id="console">PASS</div>
<embed name="plugin" src="resources/test.blinktestplugin" type="application/x-non-existent">
<script>
    if (plugin.postMessage)
        logFailure();
    finishTest();
</script>