title: Electron desktopCapture not grabbing audio from single application
body: <p>I am looking to build a voice chat application (with screenshare capability), but when using the Electron Desktop Capture plugin, the 'chromeMediaSource' parameter in audio is not taking any effect (Tested on Windows 10).</p>
  
  <p>For some reason, it is capturing the desktop audio in full, meaning that users can hear themselves when watching the screenshare.</p>
  
  <p>Is there any way to only capture one application's sound using this plugin?</p>
  
  <p>Below is the code I am using, which captures desktop audio/video.</p>
  
  <pre><code>desktopCapturer.getSources({ types: ['screen', 'window', 'audio'] }).then(async sources =&gt; {
    for (const source of sources) {
      //console.log(source);
      if (source.id === screenID) {
        try {
          const stream = await navigator.mediaDevices.getUserMedia({
            audio: {
              mandatory: {
                chromeMediaSource: 'desktop',
                chromeMediaSourceId: screenID,
              }
            },
            video: {
              mandatory: {
                chromeMediaSource: 'desktop',
                chromeMediaSourceId: screenID,
                minWidth: 1280,
                maxWidth: 1280,
                minHeight: 720,
                maxHeight: 720,
                maxFrameRate: 60
              }
            }
          })
          handleStream(stream)
        } catch (e) {
          handleError(e);
        }
        return;
      }
    }
  });
  </code></pre>