<!DOCTYPE html>
<html>
    <head>
        <script>
async function capture()
{
    try {
        const stream = await navigator.mediaDevices.getUserMedia({ audio: true, video: false });
        internals.setMockAudioTrackChannelNumber(stream.getAudioTracks()[0], 2);

        var audioContext = new webkitAudioContext();
        var analyzer = audioContext.createAnalyser();
        analyzer.fftSize = 256;
        let source = audioContext.createMediaStreamSource(stream);
        source.connect(analyzer);
        analyzer.connect(audioContext.destination);

        for (let cptr = 0; cptr < 1000; cptr++) {
          internals.setMockAudioTrackChannelNumber(stream.getAudioTracks()[0], (cptr % 2) ? 1 : 2);
          await new Promise(resolve => setTimeout(resolve, 20));
        }

        source.disconnect(analyzer);
        analyzer.disconnect(audioContext.destination);

        window.webkit.messageHandlers.gum.postMessage("PASS");
    } catch (e) {
        window.webkit.messageHandlers.gum.postMessage("FAIL: " + e);
    }
}
        </script>
    <head>

    <body onload="capture()">
    </body>
</html>