chromium/third_party/blink/web_tests/external/wpt/fullscreen/api/resources/attempt-fullscreen.html

<!DOCTYPE html>
<meta charset="utf-8" />
<title>IFrame Fullscreen API success reporter</title>
<body></body>
<script>
    window.addEventListener("message", async (e) => {
        switch (e.data.action) {
            case "report":
                await sendReport();
                break;
            default:
                parent.postMessage(
                    {
                        report: {
                            api: "fullscreen",
                            result: `Unknown action ${e.data.action}`,
                            frame: window.name,
                        },
                    },
                    "*"
                );
        }
    });

    async function sendReport() {
        let didSucceed = true;
        let error;
        let errorMessage;
        try {
            await document.body.requestFullscreen();
        } catch (e) {
            didSucceed = false;
            error = e.name;
            errorMessage = e.message;
        } finally {
            const data = {
                report: {
                    api: "fullscreen",
                    result: didSucceed,
                    frame: window.name,
                    error,
                    errorMessage,
                },
            };
            parent.postMessage(data, "*");
        }
    }
</script>