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3  window.onload = function() {
4    bc1 = new BroadcastChannel('no-cross-origin-messages');
5    bc2 = new BroadcastChannel('no-cross-origin-messages');
6    bc2.onmessage = e => {
7      parent.postMessage('done', "*");
8    };
9    // Post a message on bc1 and once we receive it in bc2, we know that the
10    // message should have been sent to bc0 if messages were being passed
11    // across origin (assuming compliance with the spec regarding message
12    // delivery in port creation order).
13    bc1.postMessage('ignition');
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16