chrome/browser/resources/net_internals/capture_view.html

<div id=capture-view-tab-content class=content-box>
  <h2>Capture options</h2>

  <p>
  <input id=capture-view-limit-checkbox type=checkbox>
  <label for='capture-view-limit-checkbox'>
    Discard old data under memory pressure.
    <i>(If you capture all events for a long time, it is possible to exhaust memory and crash. Throwing out older data avoids this problem.)</i>
  </label>
  </p>

  <p>
  <input id=capture-view-byte-logging-checkbox type=checkbox>
  <label for='capture-view-byte-logging-checkbox'>
    Include the actual bytes sent/received.
    <i>(This will result in huge log files, and can expose sensitive data)</i>
  </label>
  </p>

  <ul>
    <li>
    <b>TIP</b>: <a href="#" id=capture-view-tip-anchor>logging from the command line</a>.

    <div style="display:none; margin-top: 10px" id=capture-view-tip-div>
      Another way to capture network events is by using the command line flag:
      <blockquote>
        --log-net-log=<i>FILENAME</i> [ --net-log-level=<i>NUMBER</i> ]
      </blockquote>
      This will stream the network events directly to a file of your choosing. If you additionally want it to log the network bytes, then pass --net-log-level=0.
    </div>

    </li>
  </ul>

</div>