<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Security-Policy" content="script-src 'none'">
</head>
<body>
<script nonce="a">
window.webkit.messageHandlers.testHandler.postMessage("Subframe: A");
</script>
<script nonce="b">
window.webkit.messageHandlers.testHandler.postMessage("Subframe: B");
</script>
</body>
</html>